Implementation of Biofuels

Definitions

Water footprint: the volume of freshwater appropriated to produce the product

Green water footprint: the volume of rainwater consumed (i.e. evaporated or incorporated into the product)

Blue water footprint: the volume of surface water and ground water consumed during production processes

Water Use Efficiency: the yield of plant product (for example tonnes of grain) per unit of crop water use (megalitres of water lost by evapotranspiration)

Water Productivity of Biofuels (WPB): the amount of net biofuel energy that is produced with 1 m3 of water lost through evapotranspiration. Water productivity measures how water efficient a feedstock is.

Background

As their water supply steadily decreases, the inefficient water use of many first generation biofuels becomes a more pertinent problem to countries. Yet, because countries are looking for renewable sources of energy to supplement nonrenewable energy sources that are being depleted, biofuel production is expected to continue to increase. As developing countries look to scale up biofuel production to have a viable source of renewable energy, the choice of which biofuels to use becomes even more relevant. Many of these countries face poverty, which would be exacerbated by the use of potential food sources to produce first generation biofuels. As biofuel production continues to increase globally on a rapid scale, countries should consider how to scale up production while simultaneously conserving as much of their water supply as possible, use available land efficiently, and use feedstocks that are water-efficient and which will not take away from the available food supply. Below we explore how to make the transition towards more water-efficient biofuels, and how countries can expand their biofuel production while maintaining a steady water supply.

See Biofuels (Overview and Policy) for further background on biofuels.

Implementation

To make biofuel production a more water-efficient process, Mission 2017 proposes a 3-step overall plan that serves as the main recommendation:

Step 1. Within the next 5 years, transition away from highly water-consumptive feedstocks toward more water efficient feedstocks, such as sweet sorghum to produce ethanol and palm oil to produce biodiesel wherever possible.

Step 2. Within the next 20-30 years, transition toward lignocellulosic biofuels and other second generation biofuels. Not enough is known about the economics of these biofuels to immediately begin their implementation. More research must be done to make lignocellulosic biofuel production a less costly process, and thus more economically competitive.

Step 3. In the long term, attempt to transition toward highly water-efficient biofuels such as algae. The development of algae based biofuels is still in its infancy, and price barriers have to be overcome to make the process more commercially viable.

In addition, the following methods are also recommended for research, testing, and implementation to reduce water consumption.

Recommendation A: Using agricultural and horticultural residues and municipal solid wastes for biofuel production

Recommendation B: Shifting the admixture used in various different methods of transportation depending on the water consumption of biodiesel and that of ethanol

Recommendation C: Emphasize the importance of water consumption in all biofuel research.

Mission 2017 recommends implementing the 3 step plan and recommendations A-C concurrently, wherever possible. The 3 step plan aids countries in transitioning into more water-friendly biofuels, and provides the basic framework of the overall plan. Recommendation A uses feedstock that doesn’t have to be independently grown thus reducing the huge water inputs that growing feedstock typically requires reducing water consumption in biofuel production. Recommendation B can be used by countries to become less reliant on biodiesel in cases for which the water consumption of biodiesel production versus that of ethanol production is particularly high.

The 3-step plan

Water Productivity of Major Feedstocks, in particular sweet sorghum and palm oil

Figure 1: Water productivity or Energy in Megajoules per cubic meter of water used by plants of 9 major biofuel feedstocks (MJ m⁻³) [1]

As shown by figure 1, the water productivity of each feedstock has a large range of values. This is because water productivity is also influenced by the conditions in which the feedstock is grown. Sugar beet and rapeseed perform relatively well. Sugar beet is characterized by a high (fresh) biomass production per volume of water consumed: about double that of sugarcane. However, net energy production of sugar beet ethanol is relatively low, due to consumption of large quantities of fossil fuels during processing while in contrast, energy required for processing of sugarcane is mostly supplied by crop residues (bagasse). Rapeseed can hardly be called a water efficient crop; the favorable WPB that characterizes its biofuel product is likely attributable to a favorable net energy yield of 9.1 GJ per tonne of processed rapeseed.

Figure 1 shows that sweet sorghum is the best feedstock to use for ethanol for its water productivity in the short term. Additionally, palm oil is shown to be the best feedstock currently available for biodiesel production.

Advantages of using sweet sorghum for ethanol production

Recently, many developing countries have been giving high priority to the use of sweet sorghum in ethanol production. Advantages of sweet sorghum over corn entail higher photosynthetic efficiency, higher stress tolerance, less fertilizer requirement, rapid growth rate, ease of planting, wide adaptability and more ethanol per unit area than corn in addition to food and fodder for cattle. Cultivating sweet sorghum would produce 4 main products [2]:

grains which can be used for food production
fodder which can be used as cattle feed
sugary juice from the stalks which can be fermented to produce fuel ethanol
bagasse remaining after extraction of juice which can be used for biorefinery operations

Unlike other feedstocks such as corn, in which the ethanol-producing part of the plant is the edible corn itself, separate parts of sweet sorghum are used to produce food and ethanol: the grains can be used for food production and the stalks can be used for ethanol production. Thus, unlike the production other feedstocks such as corn, planting of sweet sorghum would supplement the food supply rather than decrease it, an important consideration for developing countries looking to invest in biofuels. Additionally, because of its efficient use of water, sweet sorghum can be cultivated in semi-arid regions where corn and sugarcane cannot be grown [2].

Based on this evidence, it is highly recommended that countries use sweet sorghum for ethanol production if they do not do so already. Many developing countries, such as India, are already looking into sweet sorghum as a viable feedstock for ethanol production [3].

Using palm oil for biodiesel production

Palm oil ranks highly in sustainability (see figure 2), in particular, water productivity (see figure 1).

Three main controversies are associated with the use of palm oil as a feedstock for biodiesel:

Deforestation: The lack of remaining land for the further expansion of the palm oil industry in the major palm oil-producing nations of Malaysia and Indonesia has led to the destruction of indigenous rainforests to expand oil palm plantations. Mission 2017 recommends that these countries stop deforestation, as the destruction of these forests has permanent negative effects on biodiversity and the carbon cycle. The value of earth’s biodiversity for future generations cannot be forgotten. We strongly recommended that countries protect their forests from the expansion of the palm oil industry by setting aside forest tracks as reserves using a combination of private and public funds effectively protecting the forests from the expansion of the palm oil industry.
Food vs. fuel: Palm oil is widely used in many developing countries for cooking. If palm oil is used for biodiesel production rather than for food, the cost of palm oil would increase significantly. However, this is a cost that some countries should be willing to pay if they face water problems.
Expansion into peat bogs: The expansion of the palm oil industry into peat bog land in countries such as Indonesia and Malaysia releases great quantities of carbon dioxide into the air, and puts a great deal of sequestered carbon into the atmosphere. Since one of the main motives in developing biofuels has been to reduce greenhouse gas emissions, these countries should cease expansion into peatland. It is strongly recommended that countries protect peat bogs from the expansion of the palm oil industry, using the same recommendations proposed for the issue of deforestation.

Figure 2: Comparing different aspects of growing various feedstocks. The set of nine sustainability indicators focus on resource use efficiency, soil quality, net energy production and greenhouse gas emissions [1]

If countries can produce palm oil without negatively affecting the environment through destruction of rainforests and peat bogs, palm oil can be used as a feedstock for biodiesel production. Oil palm plantations can be developed in tropical areas of Africa, the Americas, and Asia. As mentioned, the two largest producers of palm oil, Malaysia and Indonesia, account for 90 percent of global palm oil production and currently face controversy over deforestation because of the little remaining land they have left to expand to. This issue reminds us that despite the fact that ecosystem services of rain forests and peat bogs are invaluable, the pressure for biodiesel production is much greater than that for preserving earth’s ecological legacy.

Many African countries that are looking to invest in biofuels face issues over deforestation as well. If palm oil production is to be recommended to these countries, forests should be well-protected from the expansion of the biofuels industry. In Africa currently, palm oil is not produced on an industrial scale and is mostly cultivated by small farmers. It will take at least 10 years to produce palm oil on a scale large enough to not only fulfill local needs, but to also export [4]. It is thus recommended that these countries invest in lignocellulosic biofuels and other second generation kinds of biodiesel, which will be discussed below.

A problem with using oil palms for biodiesel production is that oil palms thrive in tropical climates but are unsuitable for growth in other regions. In particular, they are not cold-resistant, and thus unsuitable for growth in many major biofuel producing countries – specifically European Union countries. It is recommended that these countries shift towards using ethanol instead of biodiesel in whichever methods of transportation possible because all other feedstocks for biodiesel are water-inefficient. See recommendation B for more details.

Lignocellulosic biofuels

Sources for lignocellusose-based biofuels include agricultural and horticultural residues, forest residues, municipal solid waste, livestock manure, perennial grasses, bioenergy crops, aquatic plants, and paper and cotton wastes [2]. The International Energy Agency’s 2008 report predicted that commercial production of biofuels could potentially be achieved by 2015, widespread production by 2020, and be cost competitive before 2030 (see Biofuels (Overview and Policy)). It is thus realistic to expect countries to invest more in lignocellulosic biofuels by the year 2020. In the meantime, Mission 2017 recommends that research into theses fuels be increased and until it is viable countries should rely on using sweet sorghum for ethanol production and palm oil for biodiesel production.

Figure 3 shows how lignocellulosic biofuels are less water-intensive than corn based ethanol and that they rank much more closely to other forms of energy in terms of water use efficiency. For these reasons, it is important that countries transition away from first generation biofuels such as corn-based ethanol to lignocellulosic biofuels in the intermediate step.

Figure 3: the water consumed in the production of different kinds of energy [5]

Controls that need to be put in place if lignocellulosic biofuels are produced

Producing lignocellulosic biofuels on a significant scale requires a few controls:

Control 1. This is applicable only in the case in which plants are grown to produce lignocellulose for biofuel feedstock. There shouldn’t be a dramatic shift in the amount of lignocellulose harvested because doing so would ruin the carbon balance in the environment and have other negative environmental effects.

Control 2. Forests need to be managed to prevent wasting/burning potential biofuel sources. It is vital that countries create organizations to monitor the state of forests if they have not already done so.

Algae-based biofuels

The products of algae harvesting can be used to produce both ethanol and biodiesel, and the yield of oil from algae is over 200 times the yield from the best performing plant/vegetable oils. Because algae can be produced in salt or freshwater, saline, arid or dry land, algae would not compete with food crops for land and water use [6]. Its relatively short harvest cycle of 1-10 days and high energy outputs versus energy inputs ratio makes it very commercially viable [7]. The high prices currently associated with algae’s conversion into biofuels are the main force currently keeping algae from being economically competitive with traditional gasoline [7]. Because the water used in algae-based biofuels can be wastewater or saltwater (resources in abundance that would otherwise remain unused [8]) it is recommended that countries scale up algae biofuel production when doing so becomes more economically viable. Government-sponsored research into making algae-based biofuel production more cost-efficient will be crucial [9]. It has been estimated by various sources that algae-based fuel will become economically viable by the year 2020, although this estimate is still somewhat optimistic considering that algae-based biofuels development is still in its infancy [10][11]. Biofuels derived from algae may be our best hope for the future in terms of water consumption.

The effect on water supply due to implementing these changes

Transitioning to the more water-efficient feedstocks of sweet sorghum and palm oil in the short term would help countries decrease water inputs in biofuel production, although pushing forward with second and third generation biofuels is strongly recommended. Implementing recommendation #1 will be the most useful in countries that use particularly water-inefficient crops, e.g. the U.S., which uses the water-inefficient soybean crop for biodiesel production. Implementing recommendation #2, as shown in figure 2, would make biofuel production almost water-efficient as the production of other kinds of alternative energy. Algae is the most water-efficient feedstock for biofuels, although much more research must be done before widespread adoption is possible

Recommendation A: Using residues and wastes for biofuel production

It takes about a thousand times more water to produce the feedstock for ethanol than it would take to refine an equivalent volume of oil, although the amounts of water used in refining the ethanol produced from the corn and in refining oil are roughly equivalent. Given this, countries should research ways to produce biofuels from feedstocks that are already present, i.e. wastes and agricultural and horticultural residues.

A major problem with using waste as a feedstock is the wide inconsistency in the composition of these wastes from place to place [2]. Many of the main waste feedstocks, such as paper sludge, still need substantial research on how to make the process of conversion to biofuels more efficient. Mission 2017 recommends that countries looking into waste as a feedstock create a more efficient system of collecting and classifying waste to better prepare the materials for biofuel production and also do further research into how to make the process of conversion into ethanol more efficient.

Agricultural and horticultural residues (the byproducts of agricultural and horticultural production) could also be used for biofuel production, and would be an asset in reducing water consumption in biofuel production. A drawback of using these as feedstocks is that cropland also requires these residues to be returned, recycling the nutrients, and theoretically, only 15-40 percent of these residues should be taken off the field for biofuel production [2]. Using these as feedstocks would thus require fields to be managed to ensure that the appropriate quantity of residues be removed for biofuel production.

As both of these kinds of feedstock consist of “waste” materials, using them would substantially lessen the amount of water needed for biofuel production. It is recommended that countries explore the usage of these materials for biofuel production with the appropriate controls in place, although other feedstocks will also have to be used for biofuel production as countries do not produce nearly enough waste and residues to rely exclusively upon these for biofuel production. As much research still has to be done on the usage of these feedstocks, it is difficult to accurately evaluate how much using them would lessen water use in biofuel production.

Recommendation B: Changing the Admixture

Recommendation B reduces water use by changing the kind of biofuel used in transportation fuels. In the U.S., for example, corn is cultivated for ethanol production and soybean is cultivated for biodiesel production. Because the water used in growing soybean is significantly greater than that usedfor growing corn, it is recommended that transportation vehicles in the U.S. use ethanol rather than biodiesel if possible; this is not applicable for some types of vehicles like airplanes, which have to use diesel and do not have the option of using ethanol. In countries like the U.S. which use particularly water-consumptive feedstocks such as soybean, this strategy could have the effect of reducing the water use of biofuels in car fuels by at least 50 percent, as soybean is 50 percent less water-efficient than corn [12].

Recommendation C: More research upon new biofuels and evaluate their water efficiency

Although biodiesel and ethanol are the main biofuels currently being used for transportation, many other biofuels that are in the development and pilot phase could potentially prove to be more water efficient (table 1). Mission 2017 recommends that countries conduct further research into future biofuels and, if the production of these biofuels proves more water-efficient and better in quality than that of current biofuels, it is recommended that countries transition toward those biofuels.

State of production as of 2009	Biofuel Types
Industrial scale production, and being used in transport	ethanol from starch/sucrose, ETBE, biodiesel
Industrial scale production, and barely being used in transport	methane, vegetable lipids, turpentine, ethanol from wood hydrolysate
Pilot/lab stage	DME, Butanol/BTBE, biohydrogen, other hydrocarbons

Table 1: different types of biofuel production [13]

Applying these Recommendations to Major Biofuel Producing Countries

United States

The US primarily relies on corn for ethanol production and soybean for biodiesel production, both of which are important sources of food. Corn should be replaced by sweet sorghum. Sweet sorghum had already been cultivated in the U.S. on a significant scale before World War II. Phasing back to sweet sorghum for ethanol production should not thus pose a significant problem.

From Figure 1, the water productivity of sweet sorghum can be estimated as 9, whereas the average water productivity of corn is 2.5. If the U.S. transitions toward using sweet sorghum, then it would increase the water productivity of its ethanol feedstock by around 260 percent.

It is highly recommended that the U.S. phase out soybean (a very water-inefficient feedstock) and replace it with palm oil for biodiesel production. Palm oil plantations could be established in regions with the suitable climate, such as Florida, California, Georgia, Louisiana and South Carolina, to provide palm oil for biodiesel production [14].

The average water productivity of palm oil is 12.5, while that of soybean is 2.5 (see figure 1). Transitioning away from soybean and towards palm oil as a biodiesel feedstock would increase the water productivity of its biodiesel feedstock by around 400 percent.

Europe

It is possible to use sweet sorghum for ethanol production in many countries in the European Union (E.U.), although the cold climate can be an obstacle in doing so in many regions. Efforts are already underway to breed sweet sorghum for an increase in cold tolerance [15], and it is recommended that these countries research more into doing so. Countries that do not use sweet sorghum but have the capacity to do so are recommended to make the transition toward investment in sweet sorghum.

In E.U. countries, where the climate is unsuitable for growing oil palm plantations, the production of biodiesel would be much more water-intensive than the production of ethanol. In all methods of transportation where the substitution is possible, fuels should contain ethanol admixtures rather than biodiesel admixtures. The following table (table 2) shows the water footprints of ethanol produced from sugar beet compared to that of biodiesel produced from rapeseed in various kinds of transportation and demonstrates that the water footprint of ethanol is less than that of biodiesel in all key areas. If less water-intensive feedstocks such as sweet sorghum are produced for ethanol production, then the water footprint for ethanol will decrease even further. As seen in figure 2, the water productivity of rapeseed is about 50 percent of the water productivity of sweet sorghum, meaning that using sweet sorghum-derived-ethanol would save the E.U. about 50 percent of the water currently being used in the forms of transportation that the recommendation would apply to.

			WF/litre per passenger km
Transport mode	Energy source	Crop source	Green	Blue	Total
Airplane	Biodiesel	Rapeseed	142–403	0	142–403
	Bio-ethanol	Sugar beet	42–79	1–10	42–89
Car (large)	Biodiesel	Rapeseed	214–291	0	214–291
	Bio-ethanol	Sugar beet	136–257	2–32	138–289
Car (small efficient)	Biodiesel	Rapeseed	65–89	0	65–89
	Bio-ethanol	Sugar beet	23–44	0–5	24–50
Bus	Biodiesel	Rapeseed	67–126	0	67–126
	Bio-ethanol	Sugar beet	20–52	0–5	20–58
Train	Biodiesel	Rapeseed	15–40	0	15–40

Table 2: green, blue and total water footprint (WF) for different modes of passenger transport in the E.U., energy source and crop choice [16]

Addressing Countries to Which the Short Term Recommendation might not be applicable

There are 2 major classes of countries which would not be able to implement these recommendations:

1. Countries that face water scarcity and for which growing these feedstocks would be unfeasible

2. Countries in which the climate is unsuitable for growing these feedstocks

Both classes of countries will be addressed.

Countries that face water scarcity

Countries that face physical water scarcity in Africa

South Africa, Zimbabwe and Mozambique are the 3 African countries that have set target mixing levels and which are facing the issue of water scarcity, with Zimbabwe and Mozambique currently facing the issue and South Africa expected to face it soon. It is vital that these countries produce water efficient feedstock to prevent the depletion of their scarce water supplies.

Note: Zimbabwe faces a situation very similar to that of Mozambique in terms of the crops both countries grow for biofuel production, the water scarcity both countries face, and the policy that both countries have towards feedstocks grown for biofuel purposes [17]. Thus, the situations of both countries are captured by the first case: Mozambique. The second situation is that of South Africa.

Case 1: Mozambique

Jatropha is a very water-intensive biodiesel feedstock. Although it is drought-resistant, it is very water-consumptive, requiring five times as much water per unit of energy as sugarcane and corn, and nearly ten times as much as sugar beet [18].

Mozambique should encourage sweet sorghum production for bioethanol, and palm oil for biodiesel production. Sweet sorghum production is already widespread in Mozambique, but more water-intensive crops – such as cassava and sugarcane – are also currently heavily produced for bioethanol purposes.

Growing cassava and sugarcane should be discouraged and sweet sorghum production should be encouraged [19]. To do this, the government should create subsidies for sweet sorghum and reduce support for cassava and sugarcane as biofuel crops. Awareness campaigns for the positives of sweet sorghum over sugarcane and cassava should be mounted to educate farmers. Additionally, the part of the sweet sorghum plant that is used for food (the grain) is separate from the part that is used to make ethanol (the sugar-rich stalk). Because the edible portion of cassava is what is used to produce biofuels, farmers growing sweet sorghum have more economic flexibility than farmers growing cassava. A similar argument can be made to convince farmers of the economic benefit of growing sweet sorghum over that of growing sugarcane, for sugarcane can be used in ethanol production but does not produce food while sweet sorghum can both be used in ethanol production and increase the food supply.

Mozambique’s reliance on jatropha for biodiesel production is particularly bad considering that jatropha cultivation is a very water-intensive process if the amount of biodiesel produced per each jatropha plant is to be maximized. Mission 2017’s recommendation would be to substitute jatropha with oil palms, but Mozambique’s policy of not growing potential food crops for biofuel purposes hinders this. Although the policy’s intent is to prevent food prices from increasing – which is especially relevant in developing countries like Mozambique – it is also important to consider both feedstocks’ water usage because Mozambique faces water scarcity [20]. However, given the water scarcity in Mozambique, Mission 2017 discourages the use of palm oil for biodiesel production as well, given the unsuitable environment for growing oil palms.

Case 2: South Africa

In South Africa, the main feedstock considered for ethanol production is sweet sorghum, whereas for biodiesel production, the possible feedstocks are soybean, sunflower seed and canola – all food oils. However, sweet sorghum would be water-inefficient in South Africa, although it is a water-efficient crop elsewhere. For further details on South Africa, see Case Study.

In both case 1 and 2, the environment is unsuitable for oil palm cultivation because oil palms require a tropical environment to grow, which these countries lack. Producing other first generation feedstocks for biodiesel production would be highly discouraged, for the inefficient water use of these feedstocks would deplete the limited water supply of these countries. However, lignocellulosic biofuels could be the best alternative for all 3 countries – and indeed any countries facing water scarcity – if the usage of sweet sorghum is unsustainable. Although palm oil and sweet sorghum rank highly in comparison to other feedstocks in water use efficiency, it could be unsustainable for many developing countries facing water scarcity to grow these crops for biofuel production, since doing so would still be a water-intensive process. It is instead recommended that these countries research more into Recommendation A: the conversion of wastes and residues into biofuels.

Although implementing recommendation A would not entirely fulfill the current biofuel requirements of these countries, it would keep these countries from depleting their scarce water supplies. To help scale up biofuel production in a sustainable way, if doing so is at all feasible, countries would have to conduct further research into lignocellulosic biofuels and other second generation biofuels, which are expected to be produced on a significant scale by the year 2020. To reduce water use wherever possible, countries facing water scarcity should implement recommendation B and shift towards ethanol rather than biodiesel in whichever transportation methods possible.

Mission 2017 strongly discourages countries with too limited of a water supply from investing in biofuels. These countries should look at other alternative energy solutions.

Countries in which the climate is unsuitable for growing recommended feedstocks

Sweet sorghum can be grown in a wide variety of regions. However, as stated earlier, oil palms can only currently be grown in tropical areas and are unsuitable for growth in many regions. These countries should research ways to genetically modify oil palms to be more suitable for growth in regional conditions.

In the meantime, to reduce water use wherever possible, countries facing water scarcity should implement recommendation C and shift towards ethanol rather than biodiesel in whichever transportation methods possible. The solution that was recommended for the E.U. is also applicable to these countries, for the E.U. falls under this class of countries.

Conclusion

Many countries’ biofuel production leads to inefficient water usage, a problem that can be mitigated by implementing the following 3-step plan:

Step 1. Transition away from highly water-consumptive feedstocks toward more water efficient feedstocks, such as sweet sorghum to produce ethanol and palm oil to produce biodiesel wherever possible.

Step 2. Transition toward lignocellulosic biofuels and other second generation biofuels.

Step 3. In the long term, attempt to transition toward highly water-efficient biofuels such as algae.

Alongside the 3-step plan, applying the following recommendations will help countries reduce their water use in biofuel production:

Recommendation A: Using agricultural and horticultural residues and municipal solid wastes for biofuel production

Recommendation B: Shifting the admixture used in various different methods of transportation depending on the water consumption of biodiesel and that of ethanol

Recommendation C: Emphasize the importance of water consumption in all biofuel research

In many countries, such as the U.S., these recommendations can be implemented and have a substantial effect on the water consumption of biofuel production. However, as discussed, other countries cannot directly implement the first step of the 3-step plan.

Countries that face water scarcity and for which growing these feedstocks would be unfeasible should research how to make biofuel production from wastes and residues more efficient and implement recommendation B.

Countries in which the climate is unsuitable for growing oil palm trees should implement recommendation C.

Implementing these recommendations concurrently would aid countries in expanding biofuel production while simultaneously, in the long run, set countries on a track toward preserving their water supplies.

References

1. Vries, S. C., Ven, G. W. J. V., Ittersum , M. K. V., & Giller, K. E. (2010). Resource use efficiency and environmental performance of nine major biofuel crops, processed by first-generation conversion techniques. Biomass and Bioenergy, 34(5), 588-601. Retrieved from http://www.sciencedirect.com/science/article/pii/S0961953410000024

2. Jiby Kudakasseril Kurian., Gopu Raveendran Nair, Abid Hussain, & G.S. Vijaya Raghavan, (2013). Feedstocks, logistics and pre-treatment processes for sustainable lignocellulosic biorefineries: A comprehensive review. Renewable and Sustainable Energy Reviews, 25, 205-219. Retrieved from http://www.sciencedirect.com/science/article/pii/S1364032113002712

3. Reddy, B.V.S., Kumar, A. A., Ramesh S.. Sweet Sorghum: A water-saving bioenergy crop. e.g. Jet Powered Motors. pp.1-12

4. Kindergan, A. (2013). Where the Palm Trees Grow. [ONLINE] Available at: http://www.thefinancialist.com/where-the-palm-trees-grow/. [Last Accessed 11/26/2013].

5. Mielke, Erik, Laura D. Anadon, and Venkatesh Narayanamurti. Water Consumption of Energy Resource Extraction, Processing and Consumption. Tech. Cambridge: Harvard University, 2010. Print.

6. University of Nebraska-Lincoln: Crop Watch (2012). Crop Water Use Comparison of Rainfed Corn, Sorghum, and Soybean from 2009 to 2011. [ONLINE] Available at: http://cropwatch.unl.edu/web/cropwatch/archive?articleID=4835538. [Last Accessed 11/26/2013].

7. Speight, J. G. (2011). The Biofuels Handbook. Cambridge: Royal Society of Chemistry, The.

8. Demirbas, A. (2010). Use of Algae as Biofuel Sources. Energy Conversion and Management, 51(12), 2738–2749. Retrieved November 26, 2013, from http://www.sciencedirect.com/science/article/pii/S0196890410002207

9. Tiffany Stecker (2012). Algal Biofuel Sustainability Review Highlights Concerns about Water Supply. [ONLINE] Available at: http://www.scientificamerican.com/article.cfm?id=algal-biofuel-sustainability-review-hightlights-concerns-about-water-safety. [Last Accessed 11/26/2013].

10. Ziolkowska, J. R., and Simon, L. (2014). Recent Developments and Prospects for Algae-based Fuels in the US. Renewable and Sustainable Energy Reviews, 847-53. Retrieved November 26, 2013, from http://www.sciencedirect.com/science/article/pii/S1364032113006801?

11. Oilgae. “Venter estimates a 10-year timeframe for algae fuel” (2010, March 8). Retrieved from http://www.oilgae.com/blog/2010/03/venter-estimates-a-10-year-timeframe-for-algae-fuel.html

12. Sandia National Laboratories (2010). Fueling the future with fish tank residue: Sandia scientist discusses use of algae as a biofuel. [ONLINE] Available at: https://share.sandia.gov/news/resources/news_releases/fueling-the-future-with-fish-tank-residue-sandia-scientist-discusses-use-of-algae-as-a-biofuel/#.UpUN18Skp1Q . [Last Accessed 11/26/2013].

13. Huijbregts, M. A. J., & Reijnders, Lucas. (2009). Biofuels for Road Transport: A Seed to Wheel Perspective. Green Energy and Technology. Springer.

14. “Arecaceae.” Wikipedia. Wikimedia Foundation, 21 Nov. 2013. Web. 23 Nov. 2013. http://en.wikipedia.org/wiki/Arecaceae.

15. Janssen, R., Rutz, D., Braconnier, S., Reddy, B., Rao, S., Schaffert, R., Parella, R., Zaccharias, A., Rettenmaier, N., Reinhardt, G., Monti, A., Amaducci, S., Marocco, A., Snijman, W., Terblanche, H., Garcia, F. Z. “Sweet Sorghum – An Alternative Energy Crop”. WIP Renewable Energies. WIP. Web. 30 Nov. 2013

16. Gerbens-Leenes, W., and Hoekstra A.Y. “The Water Footprint of Biofuel-based Transport.” RSC Publishing. RSC, 24 May 2011. Web. 25 Nov. 2013. http://pubs.rsc.org/en/content/articlehtml/2011/ee/c1ee01187a.

17. “Zimbabwe Biofuels Report – Bioenergy Articles from The Bioenergy Site – The Bioenergy Site.” Zimbabwe Biofuels Report – Bioenergy Articles from The Bioenergy Site – The Bioenergy Site. Bioenergy Site, Dec. 2011. Web. 25 Nov. 2013.

http://www.thebioenergysite.com/articles/1103/zimbabwe-biofuels-report.

18. McKenna, P. (2009, June 9). All Washed Up for Jatropha? | MIT Technology Review. Retrieved November 29, 2013, from http://www.technologyreview.com/news/413746/all-washed-up-for-jatropha/

19. Schut, Marc. “Biofuel Developments in Mozambique: An Analysis of Policy, Potential and Reality.” Www.open.ac.uk. The Open University, 17 Mar. 2010. Web. 25 Nov. 2013. http://www.open.ac.uk/technology/mozambique/sites/www.open.ac.uk.technology.mozambique/files/pics/d128234.pdf.

20. “Mozambique: Land and Biofuels.” Www.open.ac.uk/. Open University, n.d. Web. 25 Nov. 2013. http://www.open.ac.uk/technology/mozambique/land-and-biofuels.