DEGREE PROJECT IN
TECHNOLOGY, FIRST CYCLE, 15 CREDITS
STOCKHOLM, SWEDEN 2017
sSWOT-ANALYSIS OF THE INTRODUCTION AND USAGE OF FAECAL SLUDGE AS
FERTILISER IN
AGRICULTURE IN THE
WESTERN CAPE PROVINCE, SOUTH AFRICA
FELICIA FRISE
ANNA RINGSTRÖM
KTH ROYAL INSTITUTE OF TECHNOLOGY
SCHOOL OF ARCHITECTURE AND THE BUILT ENVIRONMENT
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ABSTRACT
For future generations, securing nutrients and minimising the biochemical flows are significant challenges for humanity. Due to this, it is important to develop new phosphorous recovery methods from alternative sources to secure food production, reach sustainable development and circular economy. Secondary resources, such as sewage sludge, could compensate for the future limited supply of phosphate rocks.
This essay, done by two students from KTH Royal Institute of Technology, Stockholm, Sweden, investigates various aspects of using sewage sludge as fertiliser as a substitute to artificial chemical fertilisers from mine phosphate rock. The study was performed during eight weeks in Cape Town, South Africa, where collection of data was done through interviews and literature.
The study aimed to identify strength, weaknesses, opportunities and threats (SWOT) with focus on sustainability to recycle and recover phosphorus through faecal sludge. The SWOT-analysis was done by investigate the technology that was required in the management system, the authorisations and regulations that controls and enable the usage, the economic and socio- cultural approach and acceptance towards the usage of faecal sludge in agriculture.
The technology that was investigated was decoupled sewage system with various treatment depending on the end-use. It was identified that the technology is existing and usable but wasn’t established on the market in the region in Western Cape, South Africa. The regulation and classification system that is used by the authorities allowed usage with some restrictions but was in the study identified as an opportunity to develop and reconstruct to adapt to the new technology available today. Acceptance and approach towards the usage of faecal sludge as fertilisers differed depending on the crops grown by the cultivator, but was in general positive.
Due to the economic situation for agriculture and wine industry in South Africa, this was the most important factor for the users regarding if they would buy the product if it was available on the market.
The conclusion of the study was that the recycling of phosphorus through faecal sludge has potential, but to make an impact on the environment both regional and global, big scale recycling with municipal systems is required.
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TABLE OF CONTENTS
List of figures ... 4
List of tables ... 5
Glossary ... 6
1. Introduction ... 7
1.1Background ... 8
1.2 Aim and objectives ... 10
1.3 Methodology ... 10
2. Results ... 16
2.1 Current situation ... 16
2.3 Regulations and Framework... 19
2.3.1 Restrictions and requirements ... 19
2.3.2 GAP and organic production ... 24
2.4 Technical system and treatment ... 25
2.4.1 Solid-liquid separation ... 26
2.4.2 Dewatering ... 27
2.4.3 Further treatment ... 28
2.5 Nutrient ... 29
2.6 Social and cultural acceptance ... 31
3. sSWOT... 33
4. Discussion ... 37
5. Conclusion ... 43
6. Future work ... 44
7. Epilogue ... 45
8. Acknowledgement ... 46
9. References ... 47
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Appendix I – New Site Outlay Of Stellenbosch Wastewater Treatment Works ... 51
Appendix II – Vector attraction reduction options... 52
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LIST OF FIGURES
Figure 1. Map of South Africa, no. 3768 Rev. 6 February 2007 ... 9 Figure 2. Aspects of investigation ... 12 Figure 3. Methodology of sSWOT – a sustainability SWOT ... 13 Figure 4. Water reservoir for irrigation at the Môreson Wine Farm, Franschhoek, Western Cape Province, South Africa ... 18 Figure 5. Schematic overview of possible treatments ... 26 Figure 6. Pathogen infection cycle... 28
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LIST OF TABLES
Table 1. Stakeholders identified in the study ... 11
Table 2. Groups of crops according to the harvested and edible part of the crops ... 20
Table 3. Restrictions for agricultural use for respective category based on the microbial class of the sludge ... 20
Table 4. Comments and restrictions for agricultural use for respective category based on the stability class ... 21
Table 5. Pollution class ... 22
Table 6. Restrictions for agricultural use for respective category based on the pollution class ... 23
Table 7. General restrictions of using sludge in agriculture ... 23
Table 8. Chemical composition of fertilisers and human manure ... 30
Table 9. SWOT identified from different categories ... 33
Table 10. Final SWOT ... 36
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GLOSSARY
Agriculture: the science concerning cultivating land and the soil to raising, producing crops and farming.
Arbuscular mycorrhiza: the association formed between the roots of most terrestrial plant species and AMF.
Arbuscular mycorrhizal fungi: fungi belonging to the Glomeromycota that form Arbuscular mycorrhiza with the roots of most land plant species.
Fertiliser: any substance used to add nutrient to the soil.
Horticulture: cultivation of garden, orchard or nursery as for examples fruits, vegetables or ornamental crops.
Macronutrients: essential nutrients required by an organism in relatively large amounts, such as protein, carbohydrate and macrominerals.
Micronutrients: essential nutrient required by an organism in relatively small amounts such as vitamins, trace minerals and essential metals.
Pathogens: disease producing agent such as virus, bacterium or other microorganisms.
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1. INTRODUCTION
The earth is experiencing many changes and challenges due to human activity. According to Cordell & Neset (2014) one of the 21th century’s key global environmental challenge is phosphorus shortage linked to world’s food demand and food security. Yet this area remains relatively understudied compared to other global environmental challenges as for example climate change and water scarcity.
Essential plant nutrient for growth and maintaining high crop yields is phosphorus, together with nitrogen and potassium, and is added to the soil as fertiliser (Cordell & Neset, 2014).
There is no substitute for phosphorus in agriculture and therefore securing availability of phosphorus is crucial to global food production. The world’s agriculture, and therefore the world’s food supply, are relying on the availability of phosphorus to grow crops. (Cordell, 2010).
The phosphorus used in fertilisers today comes in particular from phosphorus reserves mined from phosphate rocks and should thus be classified as a fossil resource (Cordell, 2010). The geopolitical status of the phosphorus is also a big challenge, with reserves estimated to last between 30 and 300 years and located in few countries and on seamounts in the Atlantic Ocean and the Pacific Ocean (Cordell & Neset, 2014). Today there are five countries that control more than 86% of the world’s phosphate mines where Morocco controls almost 74% of the reserves, located in the occupied West Sahara, and South Africa control just over 2% as the fifth largest reserve. (U.S. Geological Survey, 2017). Today 90 % of the phosphorus demand is used in food production where 82% is used as fertilisers (Cordell & Neset, 2014).
The non-use of recyclable phosphorus sources and the use of mined phosphorus in artificial fertilisers, in all kind of agriculture, contributes to a phosphorus cycle that isn’t closed.
Scientists believe that, like peak oil, phosphorus might also reach its peak between the years 2033 and 2100. These predictions vary widely depending on the different methodologies, assumptions and the lack of knowledge of the amount of phosphate reserves. (Cordell & Neset, 2014).
Phosphorus is essential for plants and further on food supply but is also a pollutant and is co- responsible for eutrophic lakes, seas and other watercourses all over the world (Cordell &
Neset, 2014). In South Africa, the usage of fertilisers contributes to the scarcity of water due
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to leached to the river systems and reservoirs, which is one of the key challenges for the country (Department of Water and Sanitation, 2016).
Phosphorus together with nitrogen, called the biochemical flows, was identified as one of nine planetary boundaries in the Planetary Boundaries Framework in 2009 (Rockström, et al., 2009).
In 2015, four of these nine boundaries were crossed and the biochemical flows was one of them. (Steffen, et al., 2015).
Sludge can, besides the supply of nutrient, increase the organic content in the soil and improve the physical properties, such as water holding capacity (Snyman & Herselman, 2006). By recycling phosphorus and other nutrients through faecal sludge, the pressure on the mines can decrease and the total amount of biochemical flows may stagnate.
Faecal sludge management (FSM) is needed in both developing and developed countries. The level of the sanitation situation varies between countries and some are in greater need than others. FSM include the chain of collection, treatment and use/disposal and is a relatively new field and have traditionally received little attention but is rapidly developing and is an area of technology with high potential. (Strande, et al., 2014). In Western Cape Province, there is a potential for both expanding and developing the FSM and for developing the fertiliser usage.
The understanding and managing of the treatment and consumption by the authorities and end- users of both water and sludge is vital for water conservation and the development of the recycling of nutrients. (South African Water Research Commission, 2015).
1.1 BACKGROUND
In the background section below, general information about South Africa and soil-biology is presented to achieve a better understanding for the presented results in this study.
SOUTH AFRICA
South Africa is located at the southern tip of the continent of Africa and occupies an area of 1.219.090 km2, a map of South Africa is shown in figure 1. The country is inhabited by 54,3 million people whereof 64,8% live in urban areas. Pretoria is the executive capital, located in the Gauteng Province in the northern part of the country and Cape Town is the legislative capital, located in the Western Cape Province in the south of the country. (Central Intelligence Agency (CIA), 2017).
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The Western Cape Province is the fourth largest of the nine provinces in South Africa with a population of 6,2 million people (Statistics South Africa, 2016) and an area of 129.462 km2 (Wesgro, 2014). Agriculture is a big sector for employment in Western Cape and agricultural products accounted for 43,8% of the exports from the Western Cape in 2012, whereof grape wines were the top largest agricultural product, followed by fruits and maize (Wesgro, 2014).
The total agriculture in South Africa currently contributes to approximately 2,5% of South Africa's GDP but the whole agro-food complex contributes to 12% of the GDP (Department of Agriculture, Forestry and Fisheries, 2016).
Figure 1. Map of South Africa, no. 3768 Rev. 6 February 2007 (United Nations, 2007)
In the Western Cape Province, there is both high mountains such as Table Mountain and the Hottentots-Holland and low lands as for example the Freshwater Wetlands at Rondevlei. The most common soil types in Western Cape are granite, shale and sandstone which create the reddish and yellowish-brown soils. Due to the surrounding mountains and the Mediterranean climate the soils varies from acid, well drained, clay and sandy soils, with low organic matter.
(Wines of South Africa, 2016). Due to the climate, the decomposition of organic matter is rapid
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in South Africa which also contribute to low organic matter in the soil (Snyman & Herselman, 2006).
SOIL
Soil is one of the most biologically diverse habitats containing for example a wide range of bacteria, funguses, insects and earthworms. The soil has its own ecosystem and various symbioses and soil organisms are of high importance for making organically bound nutrients available for plants. (Bender, et al., 2016). Arbuscular mycorrhiza is a symbiosis between a fungus and the roots of a terrestrial plant and is the most widespread symbioses on earth. The fungus provides the plant with phosphorus, minerals and micronutrient, which is often more efficiently taken up by the fungus, and the plant provides the fungus with carbon from their photosynthesis. (Verbruggen, et al., 2015). The biological life in the soil influences the soil aggregation and the structure and the mycorrhiza symbiosis can reduce the leached of nutrients from the soil by increasing the uptake from the plants (Bender, et al., 2016).
1.2 AIM AND OBJECTIVES
The field study aims, with a holistic approach, to map the stakeholders linked to the use of fertilisers and investigate whether faecal sludge from a decoupled system is considered to be suitable as fertiliser in agriculture in the Western Cape Province in South Africa. This system, and the use of this kind of fertilisers, takes advantage of overload of resources and can potentially contribute to a more sustainable agriculture, reducing the use of mineral fertilisers, minimise final deposition and closing the phosphorus cycle. The aim of the field study will help to reach the objective of the study; to create a basis for future work towards a sustainable way of using phosphorous.
1.3 METHODOLOGY
STAKEHOLDER MAPPING
A stakeholder mapping was made to identify the stakeholders that can affect and/or contribute to the developing and enabling of the use of sewage sludge and/or be affected by the implementation of the product. From the identified stakeholders, interviews and a literature study were made to collect aspects and information about their part in the processes and how they potentially will be affected with an implementation.
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The identified groups of stakeholders were technical specialists, authorities and end-users which constitutes of the specific stakeholders important for the system and the use of faecal sludge fertilisers in agriculture. These identified stakeholders where afterwards categorised for a structured inventory of the system. Crops can grow in, on or above the soil which limit the contact variously with the fertilisers. This is a significant factor when discussing the usage of fertiliser and resulted therefore in three different cultivator stakeholders in the mapping of the stakeholders. The result from the stakeholder mapping is shown in table 1.
Table 1. Stakeholders identified in the study
Stakeholder Function in the
study
Actions in process
End-user Cultivator of fresh produce production grown in or on the soil
Information about their current usage, attitude, culture and economical approach
User of fertiliser
Cultivator of vine, fruit and plants grown above the soil
Information about their current usage, attitude, culture and economical approach
User of fertiliser
Cultivator of non- edible products, e.g.
plants for recreation, energy or animal consumption
Information about their current usage, attitude, culture and economical approach
User of fertiliser
Authorities Department of Water and Sanitation, South African Government
Information about regulations,
frameworks for how the sludge should be handled and further used in agriculture in South Africa
Providing restrictions and regulations Monitoring the system
Other authorities Information about regulations,
frameworks for how the sludge should be handled and further
Certifications and monitoring
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used in agriculture in South Africa
Technical specialists
Stakeholders providing decoupled sewage system
Information about the technical sewage system
Providing the decoupled sewage system
Stakeholders providing various treatments
Information about the treatment methods
Providing treatments
Municipality Information about how the wastewater treatment plants works today
Operate the municipal
wastewater treatment plants
ASPECTS OF INVESTIGATION
From the mapping of the stakeholders, aspects of investigation in the study were identified, shown in figure 2. These aspects were identified as important for the understanding of the complexity of the situation and defining the different subjects that are involved in the question of issue. The aspects were therefore seen as a good starting point for the further investigation and for achieving the purpose with the study.
Figure 2. Aspects of investigation
Technology
Legal and Regulatory Framework Socio-Cultural
Acceptance and Economical
approach
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In this study technology refers to investigate the technical system used in the process. Legal and regulatory framework explains the approaches and procedures that needs to or are suggested to be followed. The last aspects, socio-cultural acceptance and economical approach, investigates the end-user’s thoughts and requirements of fertilisers in general and human excreta in particular. The goal with the field study was to identify the strengths (S), weaknesses (W), opportunities (O) and threats (T), with the focus on sustainability (sSWOT), within the above-mentioned aspects.
SSWOT
The methodology of the sSWOT-analysis is shown in figure 3. The sSWOT analysis starts with the broad picture and the identification of the environmental challenges in the defined region and the usage of faecal sludge as fertiliser. By the end, it will lead to concrete and prioritized acts based on the identified strengths, weaknesses, opportunities and threats. (Metzger, et al., 2012).
Figure 3. Methodology of sSWOT – a sustainability SWOT
The S, W, O, T were identified by literature study and interviews described below. To achieve a larger extent of factors that might affect the system, strengths, weaknesses, opportunities and threats were first identified within various categories set up by the authors. The chosen categories were nutrient and fertiliser content, technical system, usage, economy and ecology.
The most crucial S, W, O, T from the various categories were afterwards compiled in the final SWOT. From the final SWOT the prioritized final acts were identified.
Strength and Weaknesses
The categories Strength and Weaknesses are factors that are considered mostly internal within Act
Prioritize Strengths &
Weaknesses Opportunities & Threats Envronmental Challenges and Big
Trends
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the project of using faecal sludge as fertiliser. The category strength refers to the core competences within the project. The category weaknesses instead identify the opposite core competences and highlights in what points the project is weak. The identified internal factors show the possibility of the project applied in the broader picture according to the identified environmental challenges. (Metzger, et al., 2012).
Opportunities and Threats
These two categories of factors are considered to be mostly external and could for example be factors concerning the market, consumer references or costs. Threats are identified by looking at both direct and indirect factors by the usage of faecal sludge as fertiliser in agriculture, where the indirect threats refer to impacts along the whole value chain. The defined threats could be a good start to use when identifying the opportunities with the project. The opportunities help to address and create solutions for the identified
environmental challenges in the beginning of the sSWOT. (Metzger, et al., 2012).
LITERATURE STUDY
Information regarding the three aspects of investigation; technology, social-cultural approach and regulatory framework, were partly identified through a literature study. Information about the current situation and nutrient content were also partly found trough the literature study. The literature study was based in the results from the mapping of the stakeholders. The scientific literature was found with iterative search in databases such as ScienceDirect and Google Scholar. All the literature has been analysed critically before being used to minimise for example the risk of biased sources.
INTERVIEWS
Interviews were made with the stakeholders identified in the mapping process to collect information about all the aspects of investigation. Questions were asked verbal as give-and- take questions between interviewer and interviewee. The questions were formed differently depending on the stakeholder’s position in the system and the supply chain and often questions were respondent-generated, meaning that the answer to a previous question led the interviewer to the next or an additional question. The interviews were recorded after approval from respectively interviewed stakeholder and afterwards transcribed. The transcribed interviews are available upon request to the authors.
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Due to identified requirements for the use of sludge in combination with constraints in time for the project; the main focus for the interviews was chosen to be vineyards. Cultivators of vineyards are wide spread in the Western Cape Province and wine and vine grapes are a big export source in the area. Vines are also crops preferable regarding the requirements of the usage of faecal sludge in agriculture and the reason why this stakeholder was chosen to be the focus in the study.
During the period of stay in Cape Town, it was harvest season for vines and longer public holidays which therefore resulted in problems to manage contact and to book interviews with various stakeholders. The limitation of the interviews was that they were time consuming both during the interview for both parties and afterwards for the authors to compile.
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2. RESULTS
2.1 CURRENT SITUATION
South Africa suffers from scarcity of water due to growth in water usage outpacing supply and have many eutrophication related problems due to many impoundments exhibiting high nutrient enrichment from agricultural runoff and urban discharge (Central Intelligence Agency (CIA), 2017; Department of Water and Sanitation, 2016). Extreme low dam levels, seldom rain and hot and dry summer season makes drought a major issue. Water restrictions have been implemented regarding the usage of municipal drinking water, as for irrigation and washing of vehicles. (Bronkhorst, et al., 2017; Western Cape Government, 2017). Wine production and the growth of vines and other fruit are big users of water and irrigation of agricultural areas is often necessary. Recirculation and reuse of water at these facilities is therefore often needed and used. (Schultz, 2017).
In South Africa, every municipality have a number of treatment works based on the population and the number of towns in the area. In general, in Western Cape Province and South Africa as a country, the wastewater treatment works experience high pressure and is working over their capacity, due to the increasing population and urbanisation. (Enele, 2017). From the treatment plants, the treated wastewater is released in the river systems and the sludge is often used as landfill or are sometimes treated through composting together with sawdust and other green waste. The compost is then stored for a long time or in some cases given for free to farmers to collect. This compost has often bad quality and contains stones, weeds and seeds.
(Botha, 2017).
Sludge can contain environmental toxins such as metals, dioxins and pharmaceuticals which make it not suitable for the use in agriculture due to its effect on the biology in the soil and the possible uptake by the plants and further consumption of the plant. This contamination often origin from industries, roads and hospitals. (Hansson & Johansson, 2012). Small levels of metal contamination were detected in the sludge during analyse at Stellenbosch wastewater treatment works, Western Cape Province, South Africa (Botha, 2017).
The monitoring of the system and treatment is done by the Department of Water and Sanitation once or twice a year. At the audits, it is controlled if the system is operating properly, the administrating work is done correctly and the parameters of the analysed wastewater is within
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the requirements. The sludge is analysed and classified by the municipalities and then reported to the Department of Water and Sanitation. (Enele, 2017).
The high pressure on the wastewater systems is leading to overflow of untreated water with the risk of pollution and eutrophication and expansion of the wastewater system is of high priority for the government (Enele, 2017). The wastewater treatment work in Stellenbosch is one example of a treatment works that is undergoing construction to increase its capacity (Botha, 2017). In the plan for the new treatment work in Stellenbosch there are a dewatering system, an aerobic digester and a composting slab for the sludge extracted from the system, see appendix I.
In the Western Cape Province, the majority of the farms have their own water and sewage system (Schultz, 2017). In some cases, water is treated at the facility and the remaining sludge is collected and handled by the municipality in the area. The treatment of wastewater varies between the facilities and are at some farms recycled and used for irrigation. At both Hartenberg Wine Estate and Môreson Wine Farm, the water from the wine production and sewage system are treated at the estate. The water is used for irrigation together with water from the river system. The sludge is, at both of the farms, not used on the estates at the moment of the interviews. (Coetsee & McNaught Davis, 2017; Schultz, 2017).
All the water in South Africa is owned by the government and landowners are responsible to treat and handle the water by the applied laws and restrictions. The monitoring process of these decouple systems and irrigation processes is done by the Department of Water and Sanitation and the Integrated Production of Wine (IPW). (Schietekat, 2017; Enele, 2017).
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Figure 4. Water reservoir for irrigation at the Môreson Wine Farm, Franschhoek, Western Cape Province, South Africa
During the field study, different fertilisers used on the vineyard were identified. Chemical fertilisers, organic fertilisers and fertilisers made from animal manure, mostly chicken, were used by the farmers. Other fertilising product such as LAN-fertilisers (limestone, ammonium, nitrate), which is a chemical fertiliser, were used to enrichen the soil. The choice of fertilisers on the vineyards depended, in a high extent, on economic aspects and answers from interviews showed that the interviewed farms had economical restrictions to take in to consideration when choosing fertilisers. Though the farms also expressed their willingness to achieve a more sustainable cultivation. The economic limitations and pressure is overall seen in the wine industry in South Africa today (Schietekat, 2017).
Today the fertilisers are transported to the end-users mostly in bulks and with the texture of pellets. In general, the wanted texture from the end-user stakeholders was identified as compost or in form of pellets, due to the texture of the soil in the area and its decomposition due to rain.
The pellet creates a slower release of the nutrients which is preferable to avoid nutrient leaching. Pellets also seems to be preferable by the farmers to keep the volumes of fertilisers
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low. (Coetsee & McNaught Davis, 2017; Schultz, 2017; Mutandwa, 2017; Mounton, 2017; van Zyl, 2017).
2.3 REGULATIONS AND FRAMEWORK
The usage and handling of water, wastewater and sludge require knowledge, regulations and frameworks to secure safe use and minimise the risk of pollution and contamination. In South Africa, vineyards and winemakers can become members of Integrated Production of Wine (IPW), which is an authority complied by the government to audit and help winemakers and vine growers to apply the requirements. (Schietekat, 2017). Laws and restrictions for faecal sludge management are set by the Department of Water and Sanitation. Other frameworks and regulations for growth of various crops are applied, such as the South Africa Good Agriculture Practice (SA-GAP) and National Policy on Organic Production.
2.3.1 RESTRICTIONS AND REQUIREMENTS
For a responsible use of sludge in agriculture, specific guidelines and requirements has been developed by the South African Water Research Commission. A classification of the sludge is needed before usage of the sludge in agriculture according to the South African Wastewater Sludge Classification System (Enele, 2017). The classification system is divided in three categories; microbial class, stability class and pollution class. (Snyman & Herselman, 2006).
SPECIFIC REQUIREMENTS Microbial class
The microbial class refers to determine the microbiological quality of the sludge, how to monitor it and to what extent it can be used. The microbial class is divided in three
categories; A, B and C depending on the values of faecal coliform and helminth ova in the sludge. The crops are divided in groups according to the harvested and edible parts of the crops, shown in table 2. The categories further have different restrictions depending on which type of crop that are grown in or on the soil, shown in table 3. (Snyman & Herselman, 2006).
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Table 2. Groups of crops according to the harvested and edible part of the crops (Snyman & Herselman, 2006)
Harvested and edible parts of the crop Example
Usually don’t touch the soil Different fruit trees (apple, orange, banana, grapes etc.) or grains (corn, oats, wheat etc.) Usually touch the soil Strawberries, eggplants, melons, lettuce,
cucumber
Are grown within the soil Potatoes, carrots, onions, beets
Table 3. Restrictions for agricultural use for respective category based on the microbial class of the sludge (Snyman & Herselman, 2006)
Microbial class Restrictions and requirements
A No restrictions and requirements
B Crops consumed raw may not be cultivated on soil with
microbial class B Restrictions:
Crops with edible parts that usually don’t touch the soil shall not be harvested before 30 days after the last application of sludge
Crops with edible parts that usually touch the soil shall not be harvested before 14 months after the last application of sludge Crops with edible parts that grows within the soil shall not be harvested before 20 months after the last sludge application if the sludge remains on the surface for 4 months or longer before planting or sowing
Crops with edible parts that grows within the soil shall not be harvested before 38 months after the last sludge application if the sludge remains on the surface for 4 months or less before planting or sowing
Animals shall not be fed from the land before 30 days after the last application of sludge
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Access to private areas is restricted before 30 days after last application of sludge
C Crops consumed raw may not be cultivated on soil with
microbial class C
Crops that usually touch the soil or grows within the soil shall not be cultivated on soil with microbial class C
Restrictions:
Crops with edible parts that usually don’t touch the soil shall not be harvested before 90 days after the last application of sludge
Animals shall not be fed from the land before 90 days after the last application of sludge
Access to private areas is restricted before 90 days after last application of sludge
Stability class
The stability class addresses the potential to generate odours and attract vectors. These questions typically concern the public and is therefore important for the individuals living in the area and is a social aspect to consider. The stability class is divided in three categories; 1, 2 and 3, where the classification depends on the percentage of vector attraction reduction of 1 out of 10 different possible option, see options in appendix II. According to the classifications system, at least one vector attraction reduction should be used before the sludge is applied to the land. The restrictions for the use of the sludge depends on the percentage of attraction reduction, shown in table 4. (Snyman & Herselman, 2006).
Table 4. Comments and restrictions for agricultural use for respective category based on the stability class (Snyman & Herselman, 2006)
Stability class Comment and restrictions
1 Comply with one of the options on a 90 %
basis
No restrictions
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2 Comply with one of the options on a 75 %
basis
Some additional management systems may be required
3 No stabilisation or options of the vector
attraction reduction are required Not suitable for agricultural use
Pollution class
The pollution class concerns the metal content in the sludge, shown in table 5. Depending on the content of metals, the sludge will be classified in category a, b or c, where category a has the lowest metal content and category c the highest. The different pollutant classes further have restrictions for use in agriculture, shown in table 6. (Snyman & Herselman, 2006).
Table 5. Pollution class (Snyman & Herselman, 2006)
Metals
[mg/kg sludge]
Pollutant class
a b c
Arsenic (As) Cadmium (Cd) Chromium (Cr) Cupper (Cu) Lead (Pb) Mercury (Hg) Nickel (Ni) Zinc (Zn)
< 40
< 40
< 1200
<1500
<300
<15
<420
<2 800
40 – 75 40 – 85 1200 – 3000 1500 – 4300 300 - 840 15 - 55 420
2 800 - 7 500
>75
>85
> 3000
> 4300
>840
>55
>420 >7 500
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Table 6. Restrictions for agricultural use for respective category based on the pollution class (Snyman & Herselman, 2006)
Pollution class Restrictions
a No restrictions
b Can be used in agriculture but additional analysis is required to see whether the soil have the possibility to accommodate the receiving content of the metals in the sludge
c Not suitable for agricultural use
GENERAL RESTRICTIONS AND REQUIREMENTS NOT DEPENDING THE SPECIFIC REQUIREMENTS
Besides the classification of the sludge, the guidelines also contain restrictions or requirements regarding for example treatment, storage, applications and a monitoring programme to determine whether the soil can continue receiving sludge with the same classifications, shown in table 7. (Snyman & Herselman, 2006).
Table 7. General restrictions of using sludge in agriculture (Snyman & Herselman, 2006)
Restriction/ Requirement Comment 1: Sludge storage before agricultural
use
Treated sludge for agricultural reasons must be stored in a facility with minimal
environmental impact. The sludge should be applied as soon as possible or actions
preventing odour or attract vectors should be done.
2: Sludge application rate Not exceed an application rate of 10 tons dry mass per hectare per year to not exceed the plant nutrient need.
3: Prevention of soil erosion The use of sludge should not cause soil erosion
4: Buffer zones for groundwater and/or surface water
To protect pollution of groundwater and surface water the distance from sludge application should at least be:
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- From surface water/borehole: >200m - Depth to aquifer: >5m
5: Distance from urban areas and informal settlements
Sludge should not be used in lands closer than 500 m from settlements
6: Monitoring programme The quality of the sludge is needed to be monitored and a soil monitoring programme is recommended
7: Record keeping Records and documentation must be kept by the sludge producer and user
2.3.2 GAP AND ORGANIC PRODUCTION
Good Agricultural Practices (GAP) is a non-regulatory-based practice, developed by the Food and Drug Administration (FDA) and United States Department of Agriculture (USDA), to help minimise microbial food safety hazards for fresh produce production. The GAP-guide identifies good agricultural and management practices for reducing the risk of microbial contamination in fresh produce and intend to build understanding and awareness of those practices that may be considered and incorporated. (U.S. Department of Health and Human Services, Food and Drug Administration & Center for Food Safety and Applied Nutrition (CFSAN), 1998).
The guidance document explains that the major source of contamination is associated with human or animal faeces and even small amounts of contamination, both in fertiliser and water, can result in foodborne illness. Thus, the guidance also say that properly treated manure can be a safe fertiliser if it is used with good agricultural practice and is correctly managed. Factors that influence the potential contamination of fresh crops and foodborne illness includes the type of crop and the amount of time between contamination occasion and harvest. (U.S. Department of Health and Human Services, Food and Drug Administration & Center for Food Safety and Applied Nutrition (CFSAN), 1998).
Farmers in South Africa can be certified according to the South Africa Good Agriculture Practice (SA-GAP) and the Department of Agriculture, Forestry and Fisheries (DAFF) has committed to expand the number of farmers with SA-GAP certificate (Department of Agriculture, Forestry and Fisheries, 2016).
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For organic production in South Africa, the National Policy on Organic Production needs to be applied. According to this policy it is prohibited to use modern technology and/or sewage sludge in production of organically produced crops. In the policy, it is also said that compost or composted animal manure should be used as a substitute for inorganic fertilisers.
(Department of Agriculture, Forestry and Fisheries, 2010). Indications made from the interviews in the field study showed a willingness to use sludge as fertilisers, not necessarily to get an organic certification for the produced wine, but because it is good for the environment (Mounton, 2017).
2.4 TECHNICAL SYSTEM AND TREATMENT
Before usage, the biodegradable organic matter in faecal sludge needs to be stabilised - which also is shown in the requirements above. Stabilisation means that the more readily biodegradable organic matter is putrefied, leaving more less-biodegradable, stable matter.
Stabilisation is central in order to lessen the odour, allow easy storage and treatment, lessen the oxygen demand and produce predictable characteristics of the sludge. The sludge is considered stable when no further biodegradation of carbohydrates, proteins, and sugars can be made and the sludge then consists of particles like cellulose, lignin and cellular matter from microorganism. (Strande, et al., 2014).
When the sludge is extracted from the system there are different possibilities for the after- treatment, depending on the area of use and the available demand for application of the sludge.
The biological conditions is essential to achieve good treatment and high pathogen reduction.
Stabilisation, organic load, particle size, density, dissolved oxygen, temperature, pH, water content and viscosity are properties of the sludge that are important to consider. (Strande, et al., 2014).
The treatments can be divided into three categories of mechanisms; physical, biological and chemical mechanisms, the last category is not investigated in this study. Physical mechanisms refer to solid-liquid separation and dewatering. Biological mechanisms mean the removal and transformation of organic matter, nutrients and pathogens via activity from microorganisms during composting processes. Pathogens can also be removed by UV-light as an additional treatment. Chemical mechanisms include using different add-ons, such as lime or chlorine.
(Strande, et al., 2014). A schematic overview of the different investigated treatment methods and various end-use of the fertilisers, are shown in figure 5.
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Figure 5. Schematic overview of possible treatments
2.4.1 SOLID-LIQUID SEPARATION
The most common solid-liquid separation is through gravity separation. By gravity it is possible to separate solid particles from the unbound water in the black water when the particles heavier than the water settles to the bottom. (Strande, et al., 2014). The investigated technical system to extract the faecal sludge is through the on-site technology, Sequencing Batch Reactor (SBR) process, which is a tank divided into two chambers. The anaerobic and aerobic treatment processes can be divided and explain in four steps with the purpose to separate the solids from the water and further clean the water (KLARO, 2015).
In the first chamber that the blackwater reaches, bigger solid components are being removed from the wastewater and gradually led into the second chamber, the SBR chamber, where the aeration process takes place. The aeration phase constitutes the biological treatment in the process where the sludge is activated. By alternating aeration phases and rest phases, micro- organisms can develop to treat the water with a controlled and thorough cleaning process. The next phase is called the rest phase where the activated sludge during a 90 minutes’ period will sediment to bottom of the SBR tank. This creates a clear water zone in the upper part of the tank, which is being separated from the wastewater system. This phase also returns the settled sludge back to the first chamber where the process starts over again. (KLARO, 2015).
Solid-liquid separation
Aeration and sedimentation
Dewatering
Sludge drying bed
Mechanical dewatering
Further treatment
Co-Composting
UV-treatment
Structural treatments, such
as pelletization
Enduse
Soilconditioner for fresh produce
Soilconditioner for crops grown above the soil Soilcontitioner for
non-edible products
Other (deposition, fuels, etc)
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2.4.2 DEWATERING
After the sludge thickening process when solid and liquid are separated, additional reducing of water is often necessary. Dewatering is reducing the volume of the sludge for easier further treatments. (Strande, et al., 2014). There are different procedures for the dewatering process, mentioned below.
SLUDGE DRYING BED
The sludge drying bed process is based on two principles; percolation and evaporation with main purpose to dewater the sludge. The drying beds consists of pipes and different layers of material draining out the water from the sludge. One example of material layers is gravel in the bottom, sand in the middle and on top the sludge. The sludge then dries naturally in the sun which removes the bound water in the sludge. (Wang, et al., 2007).
In South Africa, 36 % of all the sludge treatment technology in municipal wastewater plants are sludge drying beds (South African Water Research Commission, 2015). Research indicates that a 15 m3 treatment plant of drying beds would be less expensive to build than a well- developed mechanical system. It also indicates that drying beds have low operational costs when compared to advanced mechanical treatments. (Diener, et al., 2014).
MECHANICAL DEWATERING
Drying beds was an example of a natural process. Mechanical dewatering using machines processes to dry the sludge, such as centrifugation or pressing. (Strande, et al., 2014). The centrifuge process dries the sludge as it is squeezed outwards of a rotating cylinder, due to the centrifugal force. The pressing process uses mechanical parts to press the sludge against perforated walls where the water is discharged through the pores. Water is then lead in one direction and the dewatered sludge is transported in another direction for extraction. (Strande, et al., 2014).
In comparison with non-mechanical drying techniques, these processes are constrained by investment and maintenance cost, maintenance skills and dependency on electricity, but are generally more effective in time and compactness. (Strande, et al., 2014).
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2.4.3 FURTHER TREATMENT
The faecal sludge consists of large amounts of microorganisms where there is a risk that these microorganisms can be pathogenic. Exposure of untreated faecal sludge is a significant health risk for humans, either through direct contact or indirect exposure. The above mentioned physical treatments are not designed or built to reduce pathogens in the sludge, although some degradation of organic compounds may occur. Depending on the end use, the faecal sludge needs further treatment until an adequate hygiene level is reached.
The transmission and spreading of pathogens can be illustrated by an infection cycle, shown in figure 6. To prevent transmission of pathogens, the infection cycle needs to be uncompleted which for sludge could be done by the treatments below. (Strande, et al., 2014).
Figure 6. Pathogen infection cycle, modified after (Strande, et al., 2014)
COMPOSTING
Combined composting, co-composting, refers to the biological decomposition of the organic components in the sludge under controlled conditions together with organic solid waste.
(Snyman & Herselman, 2006). The process is governed by different important mechanisms such as oxidation of organic compounds, release of nutrients and microbial synthesis of new compounds. (Strande, et al., 2014).
Pathogen contaminated
sludge
Water and food contamination
Human consumption Infected
individual Pathogen-
containning faeces
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The composting process goes through three phases. In the first phase, biodegradable compounds as for example sugar, starch and protein are consumed by bacteria which leads to rapidly growing of the bacteria and the temperature in the compost starts to increase. In the second phase, the temperature in the compost system has increased to 50-75 °C. This makes thermophilic bacteria become active which continues the decomposing of the organic matter further. With higher temperatures in the system, pathogens are reduced and plant seeds inactivates. The third phase means stabilisation in the system. The bacterial activity slows down and temperature lowers due to the sugar, protein and starch are consumed. (Strande, et al., 2014).
In South Africa 19 % of all the sludge is co-composted as an additional treatment in municipal wastewater plants and is used in both metropolitan city councils as well as in smaller towns (South African Water Research Commission, 2015).
UV-TREATMENT
The biological treatment reduces active pathogens, but for further reduction additional treatment, such as UV-light, can be needed depending on the end-use. When sludge is treated with UV-light it is important that the light rays is able to penetrate the entire layer of sludge during the treatment process. High organic matter prevents penetration of UV-light which make the treatment likely to only work on the surface and leave deeper sludge untreated, if the layer is to thick. For a more effective treatment, vigorous stirring may expose all the sludge to the UV-light. (Strande, et al., 2014).
2.5 NUTRIENT
Micronutrients are essential plant minerals utilised by the crops in small quantities. Without micronutrients, the plant may not be able to utilise macronutrients, such as phosphorus, even though it is available in the soil. Iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), boron (B), molybdenum (Mo) and chlorine (Cl) are micronutrients that are essential for plants and for proper growth. (Mengel, 1990). In faecal sludge and wastewater, micronutrients such as Fe, Cu, Zn and Mn can be found (Gorazda, et al., 2017). The nutrients in the sludge are organically bounded which slowly become available to the crops through mineralisation (Mnkeni &
Austin, 2009).
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The nutrient values are geographical depending and can vary between human manure, which are important to have in mind. A study in Ntselamanzi, Alice, South Africa evaluated the amounts of nutrient in human excreta obtained from Mthatha in the Eastern Cape Province in South Africa. The human excreta were obtained from urine-diversion toilets where no water is used and the urine and faeces are separated directly in the system. In the study, the manure effectiveness as a source of micronutrients was evaluated. (Mnkeni & Austin, 2009). To compare the macronutrient values from a system more comparable to the system investigated in this study, nutrient values from a project in Slovenia were also used in the analyse.
In this study, different fertilisers were identified used by the stakeholders. On the vineyards various fertilisers were used, both chemical, organic and fertilisers made from animal manure.
The fertilisers listed in table 8 were some of the identified and analysed fertilisers from the interviews made in this study. The chemical composition of the fertilisers and the human manure is compiled in table 8 for comparison.
Table 8. Chemical composition of fertilisers and human manure a(Atlantic Fertiliser, 2016), b(Talborne Organics, 2016), c(Mulec, et al., 2016), d(Mnkeni & Austin, 2009)
Chemical composition of
Atlantic Fertiliser Bio Ganica
Atlantic Fertiliser Bio Rocka
Talbourne Fertiliser Vita-Green 5:1:5 (16)b
Talbourne Fertiliser Vita-Fruit &
Flower 3:1:5 (18)b
Human manurec,d
pH 7 - 7,1 7,7 8,5c
C [g/kg] 115 106 300 270 324,9c
N [g/kg] 26 24 73 60 36,7c
P [g/kg] 18 27 15 20 33,1c
K [g/kg] 33 30 73 100 15,8c
Ca [g/kg] 36 60 70 40 4d
Mg [g/kg] 7 6 3 5 7,9d
Mn [g/kg] 0,61 0,57 0,058 0,045 0,035d
Fe [g/kg] 5 5 0,857 0,682 0,052d
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Cu [g/kg] 0,06 0,06 0,015 0,023 0,063d
Zn [g/kg] 0,54 0,50 0,095 0,19 0,033d
As seen in table 8, human excreta contain high content of phosphorous and carbon and lower content of nitrogen compared to the examples of fertilisers used in agriculture today. The values of micronutrient also differed, where the content of calcium was significantly lower in the human manure. During the field study, the most applied nutrient to the soil, according to the interviewed farmers, was identified to be nitrogen. Apply of phosphorous to the soil was not needed as regularly due to the slow movement of the element in the soil and added if analysis of the soil showed lack of phosphorous (Mounton, 2017; Mutandwa, 2017; Coetsee &
McNaught Davis, 2017; Schultz, 2017). Faecal sludge could therefore also be seen as a complement, a phosphorous top-up instead of the main fertiliser (van Zyl, 2017).
2.6 SOCIAL AND CULTURAL ACCEPTANCE
The report Social/Cultural Acceptability of Using Human Excreta (Faeces and Urine) for Food Production in Rural Settlements in South Africa is written by Duncker, et al. (2007) as a report to the Water Research Commission. The study aimed to determine the acceptability, attitude and perceptions of using human excreta as fertiliser for food production in rural settlements both worldwide and in South Africa. The report studied different provinces and areas in South Africa, however the Western Cape Province was poorly investigated.
According to Duncker, et al., (2007), diseases related to human excreta is common in developing countries which affects the attitude towards human excreta. In China, and some countries in Africa, human excreta as fertiliser is a well-known practice and is accepted.
Attitude and perceptions against human excreta may vary between factors such as age, sex, religion and education and differ between faeces and urine.
In some provinces in South Africa there are cultural taboos and meanings attached to human excreta but according to Duncker, et al., (2007), these taboos are no great factors when analysing the implementation of certain toilets and the usage of faeces and urine in agriculture, except in the Eastern Cape Province. Factors that were significantly more common were that human excreta are seen as a waste product, are unhealthy, unhygienic and is harmful for
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humans. There were also objections of the usage due to the perception that it will have a bad odour.
The interviewed stakeholders in the study had different views towards the use of faecal sludge in agriculture. In general, few have heard about the possibility to use faecal sludge as fertilisers and the majority of the interviewed were not negative towards the practice - but it is possible to see differences in the attitude towards it. There were answers confirming the results from the earlier report mentioned above, such as the risks of odour and health hazards, but also answers that gave the opposite results. No cultural taboo could be seen and stakeholders in the system showed willingness to pay for the use of fertilisers made from faecal sludge. (Mounton, 2017; Coetsee & McNaught Davis, 2017; Schultz, 2017). However, treated faecal sludge is typically perceived differently than raw excreta and has often higher acceptance due to its structure, less smell and health impacts (Strande, et al., 2014) and could be an explanation for the relatively high acceptance within the interviewed stakeholders in the study. The interviews also showed that stakeholders preferring as a first step not to handle the sludge by themselves at the farm but was interested in using the end-product made from their sludge (Mounton, 2017;
Coetsee & McNaught Davis, 2017; Schultz, 2017).
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3. SSWOT
From the results in this study strengths, weaknesses, opportunities and threats has been identified for the SWOT analysis. To achieve a larger extent of factors that might affect the system, SWOTs were identified from different categories and aspects set up by the authors.
These S, W, O, T are shown in table 9. The most crucial strengths, weaknesses, opportunities and threats are afterwards compiled in the final SWOT shown in table 10, to be able to further prioritize the final acts, according to the methodology of a sSWOT.
Table 9. SWOT identified from different categories, identified in: literature study [l], interview [i]
Function or Stakeholder
SWOT Comment
Nutrient and fertiliser content
Strength Content of nutrients and organic matter [l]
In general, higher phosphorous content in the human manure than in the compered fertilisers used by farmers today [l]
Potentially higher pH compared to other fertilisers [l]
Weakness In general, lower nitrogen content in the human manure than in the compered fertilisers used by farmers today [l]
Potentially higher pH compared to other fertilisers [l]
Opportunities To be used as a phosphorus “top-up” [i]
Threats Might be content of heavy metals [l,i]
Technical system Strength On-site decoupled system [l]
Lower the pressure on the municipal sewerage system [l]
No chemical treatment needed [l]
Weakness Electricity depending [l]
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Opportunities Possibility to relieve the already overloaded existing sewage system [l]
Threats Not established on the market [l,i]
Usage Strength Lower the use of mined and chemical fertilisers [l]
Weakness Socio-cultural aspects that can affect the acceptance [l,i]
Big volumes if used as compost [i]
Opportunities The wastewater can be used for irrigation – contains nutrients [l]
Possible to have the fertiliser in different textures [l]
Majority of the farms in Western Cape Province has an on-site system installed [i]
Being identified as a more sustainable product [l,i]
Indication that stakeholders want to use good fertilisers because it’s good for the environment, not only necessary to get a certification [l,i]
Threats GAP and National Policy on Organic
Production prevent the usage of faecal sludge [l]
Restrictions from the South African Wastewater Sludge Classification System and cannot be used on all kind of crops [l]
Easy to access and use the non-changing chemical fertilisers [i]
No framework that “forces” farmers to work towards a more sustainable agriculture [l]
Economy Strength There are stakeholders willing to pay for fertilisers made from sludge [i]
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Weakness Investment costs for an own treatment system [l]
Opportunities Have possibility to create more locally produced fertilisers on-site, which may reduce the cost [l,i]
The service for extract, handling and treating the sludge – creates job opportunities [i]
Threats Restricted budgets - farms often need to buy the cheapest fertilisers on the market [i]
Ecology Strength Sustainable use of fertilisers [l]
Recirculation of nutrients [l]
Lower the biochemical flows [l]
Lower the eutrophication [l]
Lower leakage to the water reservoirs [l,i]
Contains organic matter, important to keep the soil alive and increase biodiversity [l]
Weakness Metals or other contents that is negative to the soil [l]
Opportunities Possibility to make stakeholders more conscious about the danger of using chemical fertilisers [l,i]
Create balance in the soil [l]
Threats The lack of knowledge about the danger of using chemical fertilisers [l,i]
The lack of knowledge and preconceptions about using faecal sludge fertilisers [l,i]
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Table 10. Final SWOT
SWOT Compilation
Strength Content of nutrients and organic matter
Contains organic matter, important to keep the soil alive and increase biodiversity
Lower the pressure on the municipal sewerage system Lower the use of mined and chemical fertilisers
Weaknesses In general, lower nitrogen content in the human manure than in the compered fertilisers used by farmers today
Electricity depending Socio-cultural aspects
Opportunities To be used as a phosphorus “top-up”
Possibility to relieve the already overloaded existing sewage system The wastewater can be used for irrigation – contains nutrients Possibility to make stakeholders more conscious about the danger of using chemical fertilisers
Threats Might contain of heavy metals
Need of establishment and acceptance on the market Regulations and framework, GAP and organic production No framework that “forces” farmers to work towards a more sustainable agriculture.
Restricted budgets - farms often need to buy the cheapest fertilisers on the market
Lack of knowledge about the threats of using chemical fertilisers The lack of knowledge and preconceptions about using faecal sludge fertilisers
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4. DISCUSSION
ENVIRONMENT
The global phosphorus demand was 2009 approximately 15 million metric tons. Scenarios for 2050 suggest an increase to a likely demand of 67 million metric tons where further calculations show that approximately 22% of this demand are available in human excreta. (Mihelcic, et al., 2011). Rockström, et al. (2009) made it clear in their report about planetary bounderies that we need to be aware about how we use natural resources. By recycling organically bounded nutrients, the biochemical flows can be lowered and by that minimising the eutrophication of land and water and secure food for future generations. This indicates that there is a need and a potential to lower the pressure on the mining industry and recycle some of the phosphorus that are in the system.
The situation in South Africa, with treatment works working over their capacity is resulting in overflows of untreated sludge and wastewater to the water reservoirs and river system. In this study, the need to lower the pressure on the municipally system it is identified. Many of the vineyards in Western Cape Province do already have a private system, and does therefore not burden the system with wastewater, but some of them transports the sludge to the municipally treatment works for disposal. By implementing treatment at the estates or at an other location, the municipally treatment works may work more efficient. This can result in less nutrient and untreated wastewater contaminating drinking water, which is a scarcity in the country.
In this study, it is not identified how efficient the majority of the sludge and wastewater are treated at the locations where decoupled system is implemented in the region and situations were untreated wastewater and sludge are disposed in the surrounding may occur. This due to factors such as the lack of monitoring by authorities and knowledge among the users about the effects of disposals, treatment methods and irrigation. Problems such as the one described above can create incentives for implementation of management and financial accounting such as information, regulation and subsidies or grants. This may support and encourage implementation of new systems, lower the disposals and increase the recirculation of nutrients.
The modern agriculture also imposes high pressure on the agroecosystem through monocultures and the application of pesticides, herbicides, fungicides and fertilisers.
Approximately 50% of the applied chemical fertilisers are absorbed by the plants and the rest is lost to leached. Nutrients can be leached below the root zone and are then not reachable by
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the plant. The loss of immobile nutrients is mainly by leached or erosion such as surfaces run off. The presence of fungus such as the arbuscular mycorrhizal fungi can increase the nutrient uptake and reduce these leaches from the soil. (Cavagnaro, et al., 2015). The mycorrhizal symbiosis is therefore an important service for the ecosystem and according to Cavagnaro, et al. (2015) it is often overlooked in the agriculture today, but can increase the yields in an environmentally sustainable way.
During the interviews in this study it was clear that chemicals were used for different purposes, both fungicides sprays and chemical fertilisers in the big scale cultivation of vines. There were vineyards that used organic fertilisers as their main product but also used chemical product, such as LAN-fertilisers, as a complement. The use of chemical substances and sprays will affect the biologically diverse in the soil and in the long run lead to a dead soil without for example earthworms and mycorrhiza. This stage is not environmental sustainable as well as economical sustainable for the future cultivation of the land. How this affect the soil and surroundings may be a lacking awareness and knowledge by the culturist. The lack of knowledge about how chemical fertilisers affect the soil, the plant and the surroundings may be a threat against the usage of other fertilisers, such as human manure. It is therefore important that this knowledge is spread within the agriculture and is prioritised when discussion further actions towards a sustainable agriculture in South Africa.
USAGE
The use of fertiliser at the interviewed vineyards varies depending on the results of the analysed leaves, grapes and soils that is regularly done on the farms. This will affect the requested amount and can lead to an unstable supply chain. In some farms fertilisers were seldom used and instead other methods of enrichen the soil with nutrients were used, such as growing nitrifying crops at the area of need and then harvest and leave for decomposing (Mutandwa, 2017).
Wine production is a science in both chemistry and agriculture. To reach your perfect wine winemakers analyse the soil and its pH-value. In some parts of the Western Cape Province the soil is acidic and needs enrichment of alkaline where some farmers use lime. (Schultz, 2017).
The pH in the fertilisers compared in this study indicates that fertilisers made from faecal sludge may reach slightly high values of pH which can be identified as both a strength and a weakness in the analysis depending on the condition of the soil.
