A
S
YSTEMATIC
L
ITERATURE
R
EVIEW
OF
B
IOFUEL
S
YNERGIES
ISRN:
LIU-IEI-R--10/0092--SE
Version 2.0, Revised since 2009
Written by:
Michael Martin and Jorge E. Fonseca A.
Linköping University
A Systematic Literature Review of Biofuel Synergies
TABLE OF CONTENTS
1 INTRODUCTION ... 2
2 AIM ... 2
3 IDENTIFICATION OF RELEVANT ARTICLES ... 3
3.1 Searching for Keywords and Combinations of Keywords ... 3
3.1.1 Step 1 – Gauging the number of relevant articles ... 3
3.1.2 Step 2- Selecting Articles for further Analysis ... 5
3.1.3 Step 3 – Categorization of articles ... 6
3.1.4 Step 4 – Obtaining selected articles/synergies ... 7
4 RESULTS ... 7
5 UNIQUE SYNERGIES FROM LITERATURE REVIEW ... 14
5.1 Ethanol Synergies ... 15
5.2 Biogas Synergies ... 15
5.3 Biodiesel Synergies from Literature Review ... 16
5.4 General Synergies in the Biofuel Industry ... 16
6 ANALYSIS AND CONCLUSION ... 16
7 REFERENCES ... 17
TABLE OF FIGURES Figure 1: Report Methodology and Steps for finding Articles ... 3
LIST OF TABLES Table 1: Combination Word Search Results ... 5
Table 2: Articles saved in each folder in Refworks ... 6
Table 3: Recurring themes of exchanges ... 7
Table 4: Biofuel to Biofuel Industry Synergies ... 8
Table 5: Biofuel to External Industry Synergies ... 10
1 INTRODUCTION
Often biofuels are criticized in the media for their low production energy efficiency, environmental impacts and by using food for fuel production. An answer most critics rely on is stating how 2nd generation biofuels will solve all the problems the first generation biofuels possess(Moore 2008a). However, 1st generation biofuels must “pave the way” for 2nd generation biofuels. They can do this by providing the infrastructure, technology and knowledge provided by the fuels.
In order to increase the efficiency of 1st generation biofuels, the theories of industrial symbiosis can be applied. Industrial symbiosis theories are designed to integrate production systems and other industries to improve energy efficiency and environmental performance(Miao and Wu 2006,Moore 2008b). By integrating biofuel production systems, the products of biofuels can be used in subsequent processes. By making use of by-products, excess heat, etc. the energy efficiency can be improved and allow for more benefits including economic and environmental performance(Mueller 2007b).
Industrial symbiosis literature includes many examples of how industries can benefit from one another but does not include much literature on the integration of biofuels. Synergies do however exist as there are many by-products which are highly prized in other industries, e.g. glycerol and DDGS. The biofuels themselves can even be used in subsequent processes. 2 AIM
The aim of producing this literature study is to find relevant biofuel synergies1 within various fields from scientific literature. By searching for keywords and combining these with keywords related to biofuel synergies we can review the extent and knowledge of synergies between external industries with biofuels, between biofuel industries and the use of their by-products throughout various research fields.
The main research questions to be answered are:
What do other research fields use biofuel by-products for?
What are the current trends for the use of biofuels and their by-products?
What substrates/by-products/wastes from other industries can be used for biofuel production?
Which synergies exist in the literature beyond those presented in other phases of the research project?
What are some potential uses for biofuels, their by-products and industrial wastes and utilities to integrate in symbiosis?
3 IDENTIFICATION OF RELEVANT ARTICLES
This report is based on an extensive systematic literature review of relevant literature for biofuel synergies, i.e. the handling of by-products between biofuel industries and external industries. The systematic literature review process was used due to its applicability in this context to allow for possible exclusion and inclusion of relevant articles based upon a clinical question, in this case finding biofuel synergies(Green et al 2006). The literature review was carried out in a step-by-step manner in order to exclude non-relevant literature from the abundance literature on the subjects.
3.1 Searching for Keywords and Combinations of Keywords
Figure 1: Report Methodology and Steps for finding Articles
3.1.1 Step 1 – Gauging the number of relevant articles
The first step of the literature review was to review how many articles were available for the topics of biogas, bioethanol, biodiesel and thereafter biofuel and to provide a “pool” of articles for later analysis. The literature review was carried out using the Science Direct scientific database search engine (reference to science direct). No other search engines were used to find articles due to the time limits of the research project and extent of literature available from the Science Direct database. The searching criteria was limited to the following constraints:
Step 4: Final Review Step 3: Categorized Themes Step 2: Exclusion of 2ndGeneration Biofuels Step 1-B: Keyword + Combination words
Dates: From: 2000 To: present 2012 Include: Journals and all books Source: All sources
Subject: All sciences
Term within: Abstract, title and keywords
A search was conduced for articles concerning biogas, ethanol(bioethanol), biodiesel and biofuel articles. This led to a total of 1150, 20050(471), 1553 and 1699 number of articles for each topic respectively. A total of 24,452 articles were therefore available in the field. Based on the methodology of a systematic literature review, exclusion categories were thereafter applied, which are described in the following sections.
It was apparent that combination words were necessary to narrow the focus of the literature. Combination words were then used, to find relevant articles under each topic for biofuel synergies, i.e. relevant articles for all topics; biogas, bioethanol, biodiesel and biofuel.
Combination words to include with each topic keyword included: Allocate; Allocation; by-product; byproduct; cooperation; co-product; coproduct; exchange; incorporate; incorporation; integrate; integration; symbiosis; synergy; synergies; share; sharing; substitute; substitution; substrate; residue; and utility.
These combination words were chosen as they represent interaction between biofuels and external industries and could provide necessary literature for this study. Table 1 below shows a review of the number of articles found for each combination of search words.
Table 1: Combination Word Search Results Compiled (2000-Present)
Main Keywords
Combination Words Biofuel Biodiesel Ethanol (26,412) Biogas
3,211 3,148 Bioethanol (1,007) 1,864 symbiosis 2 1 6 7 synergy 15 8 35 5 cooperation 14 7 21 5 by-product 651 684 3368 245 byproduct 127 112 415 78 co-product 156 119 684 57 exchange 63 94 599 17 Share 80 27 96 27 sharing 0 0 31 2 substitute 100 132 158 44 substitution 66 42 311 35 allocation 48 15 39 10 integrate 17 5 31 6 integration 111 45 187 33 incorporate 14 4 41 5 incorporation 25 24 302 6 substrate 202 158 1782 305 residue 258 120 647 158 utility 24 11 135 80 Total Number: 1973 1608 8888 1125
Upon finding the number of articles for each topic and combination word, further exclusion criteria were applied to produce relevant literature and narrow the number of articles for this study. As can be seen in Table 1, there are many articles provided for each topic; especially for ethanol. However, for some keyword+combination word searches, only a limited number of articles were returned. To finalize Step 1, some of the combination + keyword searches were disregarded from the previous listing of combination words. Those include the combination words, synergies, coproduct and allocate; which are not present in Table 1.
3.1.2 Step 2- Selecting Articles for further Analysis
Step 2 of the literature search was conducted in order to limit the number of articles and provide relevant articles for further in depth analysis in Steps 3 and 4. Following a review of the articles in each of these combination topic + keyword searches, many themes emerged for each respective biofuel topic. Many articles contained information about chemical experiments, second generation biofuels and hydrogen production which are beyond the scope of this study. The following exclusion criteria were thus applied in order to confine the literature to first generation biofuel production and interaction between biofuels and external industries for each respective biofuel topic.
Biodiesel
Exclude 2nd Generation Biofuels i.e. Fischer-Tropsch and other synthetic diesel
Biogas
Exclude 2nd Generation Biofuels i.e. steam reforming and gasification of biomass
Ethanol
Exclude 2nd Generation Biofuels i.e. cellulosic ethanol
Exclude articles about ethanol used for hydrogen fuel cells Biofuel
Exclude 2nd Generation Biofuels i.e. all second generation biofuel articles
In some of the cases as shown above, there were over 1,000 articles for each topic and combined keyword respectively. After excluding the topics as aforementioned, the first 150 articles from the total listing in those cases where there were over 150 were reviewed and saved if relevant.
Articles that were considered relevant after the exclusion categories were saved in a referencing database, Refworks. Refworks was used due the ease of exporting citations and providing links back to the articles for subsequent steps. All articles were saved in a respective folder under that theme, i.e. there were 4 folders created which were labeled biofuel, biogas, ethanol and biodiesel. The number of articles contained in each folder are shown below in Table 2.
Table 2: Articles saved in each folder in Refworks
Biodiesel Biogas Bioethanol Biofuel Number of
Articles 91 196 66 138
3.1.3 Step 3 – Categorization of articles
The next step for limiting the number of articles and finding relevant articles was to categorize the articles in order to find if there were recurring themes. An in depth review of all abstracts was conduced from the articles reviewed in Step 2. These abstracts and articles were categorized based on their themes. During the process it was found that some of the articles were redundant or doubled in several folders and were therefore deleted before proceeding to the categorizing them. The categories for each folder can be seen in Table 3.
Table 3: Recurring themes of exchanges Categories Food/Feed Biogas Energy/Fuel Municipal Biodiesel Algae Chemical/Cosmetics Agriculture Ethanol Greenhouse Environmental Services Materials/Building Biofuel General Forestry/Paper
The list of all references and articles contained in Table 3 are listed in Appendix A-D 3.1.4 Step 4 – Obtaining selected articles/synergies
A final listing of relevant articles was produced for Step 4 of the literature review. Once the articles were divided into categories the abstracts were reviewed for further relevance. Articles which contained information about integration of biofuel processes, making use of by-products and using residues and by-products of other industries for biofuel production were included in the final list.
Many articles were found to contain similar contents, i.e. from the categorized themes from Step 3. For example, many articles describe the use of biomass for biofuel production. Consequently, only a selected few in the case where many similar articles are present were selected for the final list. Thereafter, articles found under the biofuel heading have been split into their relevant categories. They contain synergies for the bioethanol, biogas and biodiesel categories and have therefore been added to each respective folder and list. The results of the final listing can be seen in Table 4 in the subsequent text.
4 RESULTS
Shown below in Tables 4-6are the final listings for the synergy articles obtained from the said literature review. Table 4 consists of all synergies regarding biofuel synergies between biofuel industries, while Table 5 contains synergies originating with products/utilities from biofuel industry shared with external industries and finally Table 6 provides synergies originating from External Industries used for biofuel production.
Table 4: Biofuel to Biofuel Industry Synergies Biofuel Biofuel Synergy From Literature Review (Martin and Fonseca 2012) By‐Product/ Utility Interaction Corn Oil for biodiesel production (Saunders
and Rosentrater 2009) By‐Product Ethanol‐Biodiesel Ethanol DDGS and syrup for biogas production
(Saunders and Rosentrater 2009) By‐Product Ethanol‐Biogas Ethanol stillage as biogas source (Doušková et
al 2010,Wilkie et al 2000) By‐Product Ethanol‐Biogas Ethanol production heat used for biogas process (Odhiambo et al 2009,Pfeffer et al 2007) By‐Product Ethanol‐Biogas Oil cake as biogas source (Ramachandran et al 2007) By‐Product Biodiesel‐Biogas Glycerol to biogas production (Siles López et al
2009,Yazdani and Gonzalez 2007a) By‐Product Biodiesel‐Biogas Glycerol used to produce ethanol (Liu et al
2012) By‐Product Ethanol‐Biodiesel
Anaerobic digestion of microalgae residues
from biodiesel production (Ehimen et al 2011) By‐Product Biodiesel‐Biogas Ethanol production from biodiesel by‐
products (Visser et al 2011) By‐Product Biodiesel‐Ethanol Biogas production of ethanol by‐products (De
Paoli et al 2011) By‐Product Ethanol‐Biogas Integrated ethanol, cattle production and
biogas to close material loops (DeVuyst et al 2011)
By‐Product Ethanol‐Biogas
Industrial CO2 used for methanol production
(Pontzen et al 2011) by‐Product Biofuel General‐Biofuel General Ethanol used as alcohol for biodiesel
production (Quintella et al 2012) By‐Product Ethanol‐Biodiesel Integrating biofuel production to produce
ethanol, biogas and biodiesel (Martin and Eklund 2011)
By‐Product Biofuel General‐Biofuel General
CO2 from ethanol production used for algae
for biodiesel production (Powell and Hill 2010) By‐Product Ethanol‐Biodiesel Ethanol Stillage used for Biogas Production
and CO2 used for algae (Doušková et al 2010) By‐Product Ethanol‐Biogas
From Brainstorming Workshop (Martin et al 2009) By‐Product/ Utility Interaction Exhaust emissions from Biogas Producer sent to Ethanol Producer for combustion/Odor Control Utility Biogas‐Ethanol Sulfur is a bad input for biogas production. Need a better way to control pH at Ethanol Producer. Biogas Producer prefers Nitrogen instead of Sulphur By‐Product Ethanol‐Biogas
Biogas used for electricity production for
biodiesel production By‐Product Biogas‐Biodiesel Refine the digestate to extract fatty acids and
phosphor By‐Product Biogas‐Biodiesel
Gas produced at Ethanol Producer ‐ Sent to
Biogas Producer for upgrading Utility Ethanol‐Biogas Gas produced at Ethanol Producer ‐ Used for
odor control/combustion process Utility Ethanol‐Ethanol Exhaust emissions from Ethanol Producer
used to dry biogas digestate Utility Ethanol‐Biogas Fusil/Other Alcohols from Ethanol Still used
for biodiesel production By‐Product Ethanol‐Biodiesel Ethanol used for Biodiesel Production By‐Product Ethanol‐Biodiesel Oil from Wheat/Corn/Other starch crops for ethanol, pressed, oil expelled and used for biodiesel before crops sent for fermentation to ethanol By‐Product Ethanol‐Biodiesel Pelletizer at Ethanol Producer employed with Digestate from Biogas Producer to make biomass pellets for fuel or feed Utility Ethanol‐Biogas Biomass from ethanol production (other than
stillage) used for biogas production By‐Product Ethanol‐Biogas Use stillage for biogas production only By‐Product Ethanol‐Biogas Glycerol produced from biodiesel production
for biogas production By‐Product Biodiesel‐Biogas Glycerol (Biodiesel by‐product) + Fatty Acids (Biogas by‐product) used for creation of monoglycerides for production of Biodiesel Feedstock By‐Product Biogas‐Biodiesel Seed cake and shells from biodiesel processing
could contain starch and thus make ethanol By‐Product Biodiesel‐Ethanol C02 from biofuel production used for algae for
Biofuel Production By‐Product Biofuel General‐Biofuel General Waste heat from ethanol and biogas facilities
used in biodiesel production Utility Ethanol‐Biodiesel Pinch Analysis for possible excess heat &
cooling between biofuel industries (Biorefinery/Cooperation)
Utility Biofuel General‐Biofuel General
Waste heat from ethanol production used for
pre‐heating of materials Utility Ethanol‐Ethanol
Table 5: Biofuel to External Industry Synergies
Biofuel External Synergies From Literature Review (Martin and Fonseca 2012) By‐Product/ Utility Interaction Ethanol DDGS for human food applications
(Champagne 2007,Robinson et al 2008) By‐Product Ethanol‐Food/Feed DDGS for animal feed (Robinson et al
2008,Klopfenstein et al 2007) By‐Product Ethanol‐Food/Feed Integration with Extrusion technology for food/fodder production (Klopfenstein et al 2007) Utility Ethanol‐Food/Feed DDGS used as filler for bioplastics (Saunders and Rosentrater 2009,Klopfenstein et al 2007) By‐Product Ethanol‐Materials/Building Ethanol By‐Products for Fertilizer Production
(Saunders and Rosentrater 2009) By‐Product Ethanol‐Agriculture Ethanol By‐Products for Construction materials
(Saunders and Rosentrater 2009) By‐Product Ethanol‐Materials/Building Biogas digestate used as solid fuel (Kratzeisen
et al 2010) By‐Product Biogas‐Energy/Fuel Digestate used as particle board fibers (Zheng
et al 2009,Zheng et al 2009) By‐Product Biogas‐Materials/Building Digestate used as fertilizer (Sager 2007) By‐Product Biogas‐Agriculture Biogas digestate used as feed (Sehgal and
Sehgal 2002) By‐Product Biogas‐Food/Feed Biodiesel by‐products used as carbon
filters(Nunes et al 2009,Foo and Hameed 2009) By‐Product Biodiesel‐Env. Services Biodiesel used as remediation agent for
treatment of oil spills (Fernández‐Álvarez et al 2007)
By‐Product Biodiesel‐Env. Services
Glycerol used as animal feed (Donkin et al
2009a) By‐Product Biodiesel‐Food/Feed
Glycerol used to produce hydrogen (Slinn et al
2008,Sánchez et al) By‐Product Biodiesel‐Energy/Fuel Glycerol used as gasoline additive (Kiatkittipong
et al 2010) By‐Product Biodiesel‐Energy/Fuel Glycerine used as a fuel (McNeil et al) By‐Product Biodiesel‐Energy/Fuel Glycerol used for combustion (Bohon et al 2011) By‐Product Biodiesel‐Energy/Fuel Biofuel by‐products (DDGS; rapeseed cake and digestate) for combustion (Piotrowska et al 2011) By‐Product Biofuel General‐Energy/Fuel Conversion of glycerol to glycolipids (Liu et al 2011) By‐Product Biodiesel‐Chemical/Cosmetics Chitin‐glucan complex production from
biodiesel by‐products (Chagas et al 2010) By‐Product Biodiesel‐Chemical/Cosmetics Biofuel production residues used as soil
amendments (Gell et al 2011) By‐Product Biofuel General‐Env. Services Glycerol used as dust suppressant (Medeiros et
Glycerol used as carbon source to produce
biosurfactant (de Sousa et al 2011) By‐Product Biodiesel‐Chemical/Cosmetics Glycerol and spent earth from biodiesel
production used to produce clay bricks (Eliche‐ Quesada et al)
By‐Product Biodiesel‐Materials/Building
Biogas digestate used as solid fuel (Kratzeisen
et al 2010) By‐Product Biogas‐Energy/Fuel Sugarcane ethanol by‐products used as cattle
feed (Egeskog et al 2011) By‐Product Ethanol‐Food/Feed Distillers dried grain with solubles (DDGS) used
in cornbread production (Liu et al 2011) By‐Product Ethanol‐Food/Feed Ethanol used as dyeing agent for textiles
(Ferrero et al 2011) By‐Product Ethanol‐Chemical/Cosmetics Sweet corn tassels from ethanol production used as replacement to peat moss in greenhouses (Vaughn et al 2011) By‐Product Ethanol‐Agriculture Wheat protein, in aqueous ethanol, used for production of particle‐bonding composites (Sanghoon 2011) By‐Product Ethanol‐Materials/Building By‐products from ethanol and biodiesel production used for biocomposites (Diebel et al 2012) By‐Product Biofuel General‐ Materials/Building Combustion of DDGS as a fuel source (Saunders and Rosentrater 2009,Doušková et al 2010) By‐Product Carbon dioxide from biogas upgrading for
greenhouses/plant source (Jaffrin et al 2003) By‐Product Biogas‐Greenhouse Biogas digestate used for vermitechnology
(Surindra 2010) By‐Product Biogas‐Agriculture
From Brainstorming Workshop (Martin et al
2009)
By‐Product/
Utility Interaction
Digestate and CO2 used as fertilizer/nutrients in
greenhouses By‐Product Biogas‐Greenhouse Dry digestate and use it as fodder By‐Product Biogas‐Food/Feed Digestate used as bio‐fertilizer By‐Product Biogas‐Agriculture Separate nutrients in digestate for chemical
processing By‐Product Biogas‐Chemical/Cosmetics Gases other than methane and CO2 captured
and stored (e.g. H2)
By‐Product Biofuel General‐ Chemical/Cosmetics C02/Water from Ethanol production for Algae
Production Utility Ethanol‐Algae
Wet Stillage used for Animal Feed Direct (no
drying) Utility Ethanol‐Food/Feed
Dry stillage for biofertilizer By‐Product Biogas‐Agriculture Waste water used for algae cultivation Utility Biofuel General‐Algae Glycerol used as binding agent for wood pellets By‐Product Biodiesel‐Energy/Fuel Use stillage for pellet production (energy) By‐Product Ethanol‐Energy/Fuel Glycerol for healthcare and cosmetics industry By‐Product Biodiesel‐Chemical/Cosmetics
"Swedish Eco‐Soap"
Glycerol used as a carbon source in biological
cleaning steps By‐Product Biodiesel‐Env. Services C02 trapped from Ethanol, Biogas production
for Greenhouses By‐Product Biofuel General‐Greenhouse C02 trapped from Ethanol, Biogas production
used for synthetic fuel production By‐Product Biofuel General‐Energy/Fuel C02 capture at Ethanol and Biogas Plants By‐Product Biofuel General‐
Chemical/Cosmetics Waste water from biodiesel or ethanol
production used for Salix production By‐Product Biofuel General‐Agriculture Waste heat from ethanol, biodiesel and biogas
production used in swimming pools/swim halls Utility Biofuel General‐Municipal Waste heat from ethanol, biodiesel and biogas
used in nearby greenhouses Utility Biofuel General‐Greenhouse
Table 6: External to Biofuel Industry Synergies
External ‐‐> Biofuel Synergies From Literature Review (Martin and Fonseca 2012) By‐Product/ Utility Interaction Bioethanol from food residues (bread, kitchen wastes, etc.) (Marques et al 2008,Ebrahimi et al 2008,Tang et al 2008) By‐Product Food/Feed‐Ethanol Paper sludge for ethanol production (Martin
et al 2009) By‐Product Forestry/Paper‐Ethanol Cheese whey lactose for ethanol production
(Guimarães et al 2010,Zafar and Owais 2006,Kargi and Ozmıhcı 2006)
By‐Product Food/Feed‐Ethanol
Biomass Wastes as biogas source
(Kryvoruchko et al 2009) By‐Product Forestry/Paper‐Biogas Food industry wastes as biogas source (Rani
and Nand 2004,Nieves et al 2011) By‐Product Food/Feed‐Biogas Fruit industry wastes as biogas source
(Llaneza Coalla et al 2009) By‐Product Food/Feed‐Biogas Animal by‐products as biogas source (Hejnfelt
and Angelidaki 2009,Mueller 2007a) By‐Product Food/Feed‐Biogas Dairy wastes as biogas source (Göblös et al
2008) By‐Product Food/Feed‐Biogas
Processing waste water for biogas production
(Stoica et al 2009) By‐Product Municipal‐Biogas Algae for biodiesel production (Bastianoni et al
2008,Brennan and Owende 2010) By‐Product Algae‐Biodiesel Biodiesel from waste oils (Chung et al
2009,Haas 2005a,Lin and Li 2009) By‐Product Food/Feed‐Biodiesel Biodiesel from sewage sludge (Angerbauer et
al 2008,Pokoo‐Aikins et al 2010) By‐Product Municipal‐Biodiesel Biodiesel production from tall oil fatty acids
(White et al 2011) By‐Product Forestry/Paper‐Biodiesel Meat industry residues for biodiesel
production (Toscano et al 2011,Jørgensen et al 2012,Andersen and Weinbach 2010)
By‐Product Food/Feed‐Biodiesel
Municipal Sewage Sludge for Biogas
Production (Tezel et al 2011) By‐Product Muncipal‐Biogas Ley crops used for biogas production (Blokhina
et al 2011) By‐Product Agriculture‐Biogas Anaerobic digestion of household food waste (Bernstad and la Cour Jansen 2011,Krzystek et al 2001) By‐Product Municipal‐Biogas Integration of ethanol production into a combined heat and power plant (Starfelt et al 2010) Utility Energy/Fuel‐Ethanol Wastewater algae used to produce acetone, By‐Product Algae‐Ethanol
MeOH, Prop‐OH, etc.
Potato Chip/Snack Food waste vegetable oil
(WVO) used for biodiesel production By‐Product Food/Feed‐Biodiesel Potato Chip/Snack Food by‐products (organic)
used for biogas production By‐Product Food/Feed‐Biogas Potato Chip/Snack Food by‐products (Potato
Skins) used for ethanol production By‐Product Food/Feed‐Ethanol Animal fats from slaughtering at nearby farm
used for biodiesel By‐Product Food/Feed‐Biodiesel Animal Wastes from farm used for biogas
production By‐Product Food/Feed‐Biogas Algae used for oil press, oil extracted for
biodiesel production By‐Product Algae‐Biodiesel Algae used for oil press, oil extracted for biodiesel production, algae then used for later ethanol fermentation and subsequent biogas processes By‐Product Algae‐Biogas Synthetic diesel Production produces alcohol as a by‐product, this can be used for biodiesel production or biogas production By‐Product Energy/Fuel‐Biodiesel Collaboration with municipal fat collector for
biodiesel production By‐Product Municipal‐Biodiesel Use fat separators from car washes,
restaurants, etc. for biodiesel production (if quality is low, for biogas production)
By‐Product Municipal‐Biodiesel
Flour production must separate all oil in flour
to increase shelf‐life. Used for biodiesel. By‐Product Food/Feed‐Biodiesel Algae from Baltic Sea used for biogas
production (Basically a free raw material) By‐Product Algae‐Biogas Household wastes for biogas production
(organic material ‐‐> Biogas) By‐Product Municipal‐Biogas Household wastes for ethanol production
(fruits, shells, etc. ‐‐‐> ethanol production) By‐Product Municipal‐Ethanol Other industries with WVO used for Biodiesel
production By‐Product Food/Feed‐Biodiesel
5 UNIQUE SYNERGIES FROM LITERATURE REVIEW
From the aforementioned synergies/articles the following lists have been produced to provide a summary of all unique synergies. When several synergies are of a similar theme, they have been summed into one type of unique synergy, although the feedstocks may be very different. For example, food industry synergies can be of many different types including fruits, vegetables, fats, dairy, etc.
5.1 Ethanol Synergies
Ethanol DDGS for human food applications (Champagne 2007,Robinson et al 2008) DDGS for animal feed(Llaneza Coalla et al 2009,Mueller 2007a)
Integration with Extrusion technology for food/fodder production(Llaneza Coalla et al 2009)
DDGS used as filler for bioplastics(Saunders and Rosentrater 2009,Llaneza Coalla et al 2009,Kale et al 2007,Karinen and Krause 2006)
Combustion of DDGS as a fuel source (Saunders and Rosentrater 2009,Doušková et al 2010)
Corn Oil for biodiesel production(Saunders and Rosentrater 2009) Fertilizer Production (Saunders and Rosentrater 2009)
Construction materials(Saunders and Rosentrater 2009,Kale et al 2007,Karinen and Krause 2006)
Bioethanol from food residues (bread, kitchen wastes, etc.(Marques et al 2008,Ebrahimi et al 2008,Palmarola-Adrados et al 2005))
Paper sludge for ethanol production(Tang et al 2008)
Cheese whey lactose for ethanol production(Guimarães et al 2010,Zafar and Owais 2006,Kargi and Ozmıhcı 2006)
Ethanol DDGS and syrup for biogas production(Saunders and Rosentrater 2009)
5.2 Biogas Synergies
Biomass Wastes as biogas source(Kryvoruchko et al 2009) Biogas digestate used as solid fuel(Kratzeisen et al 2010) Digestate used as particle board fibers (Zheng et al 2009) Household wastes as biogas source(Krzystek et al 2001) Food industry wastes as biogas source(Hou and Zheng 2009)
o Fruit industry wastes as biogas source(Llaneza Coalla et al 2009)
o Animal by-products as biogas source(Hejnfelt and Angelidaki 2009,Mueller 2007a)
o Dairy wastes as biogas source (Donkin et al 2009b)
Carbon dioxide from biogas upgrading for greenhouses/plant source(Jaffrin et al 2003) Ethanol stillage as biogas source(Doušková et al 2010,Wilkie et al 2000)
Digestate used as fertilizer (Sager 2007)
Ethanol production heat used for biogas process(Odhiambo et al 2009,Pfeffer et al 2007) Municipal solid wastes as biogas residue(Haas 2005b)
Processing waste water for biogas production(Stoica et al 2009) Oil cake as biogas source(Ramachandran et al 2007)
Biogas digestate used as feed (Sehgal and Sehgal 2002) Ley Crops for biogas production (Blokhina et al 2011) Biogas digestate used to worm farming (Surindra 2010)
5.3 Biodiesel Synergies from Literature Review
Biodiesel by-products used as carbon filters(Fernández-Álvarez et al 2007,Encinar et al 2007,Fernando et al 2007)
Glycerol to biogas production(Siles López et al 2009,Yazdani and Gonzalez 2007b,Shams Yazdani and Gonzalez 2008)
Biodiesel used as remediation agent for treatment of oil spills(Burström and Korhonen 2001)
Algae for biodiesel production(Chertow 1999,Wan Ngah and Hanafiah 2008) Glycerol added to gasoline as fuel extender (Kiatkittipong et al 2011)
Biodiesel from waste oils (WVO, fish oil, animal tallow, etc.)(Chung et al 2009,Haas 2005a)
Glycerol used to produce hydrogen (Slinn et al 2008,Fountoulakis and Manios 2009) Glycerol used to produce ethanol, formate and hydrogen(Swedish Biogas International
2009)
Biodiesel from sewage sludge(Demirbas 2000,Börjesson 2006)
Glycerol as automotive fuel (Fernando et al 2007,Kiatkittipong et al 2011) Glycerol used as animal feed(Donkin et al 2009a)
Meat industry by-products for biodiesel production (Toscano et al 2011,Jørgensen et al 2012,Andersen and Weinbach 2010)
5.4 General Synergies in the Biofuel Industry
Integration with CHP Plant (Starfelt et al 2010)
6 ANALYSIS AND CONCLUSION
The literature review produced a large number of possible synergies to handle external and biofuel by-products. Among the 123 final synergy articles produced, biogas synergies seem to be a very popular option for the handling of industrial wastes and biomass. Algal biofuels were not as apparent as originally thought though some applications have been provided for the production of oil for biodiesel. Biodiesel synergies consisted primarily of the handling of waste oils for biodiesel production and the use of glycerol for a wide array of applications from vehicle fuel to filters. In the production of ethanol, the use of DDGS for various applications is very common and many possible synergies were produced. However, not many further applications for ethanol by-products have been uncovered though several articles deal with the use of different raw materials (which are industrial by-products) for the production of ethanol.
Furthermore, there seems to be a large number of articles concerned with the production of hydrogen from the biofuels themselves, especially for the production of ethanol in various forms and thereafter utilizing the ethanol to produce hydrogen. Only one of these articles was highlighted for this literature review. Beyond hydrogen production, 2nd generation ethanol production was plentiful in the literature.
7 REFERENCES
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