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One of the important concerns about wide scale development of biodiesel is if it would displace croplands currently used for food crops. With algae, that concern is completely eliminated, as algae grows ideally in either hot desert climates or off of waste streams. NREL's research focused on the development of algae farms in desert regions, using shallow salt water pools for growing the algae. Another nice benefit of using algae as a food stock is that in addition to using considerably less water than traditional oilseed crops, algae also grows best in salt water, so farms could be built near the ocean with no need to desalinate the seawater as it is used to fill the ponds.
NREL's research showed that one quad (ten billion gallons) of biodiesel could be produced from 200,000 hectares of desert land (200,000 hectares is equivalent to 780 square miles). In the previous section, we found that to replace all transportation fuels in the US, we would need 140.8 billion gallons of biodiesel, or roughly 14 quads. To produce that amount would require a land mass of almost 11,000 square miles. To put that in perspective, consider that the Sonora desert in the southwestern US comprises 120,000 square miles. As can be seen in Figure 1 below, the Sonora desert is located along the Pacific ocean, making it an ideal location for algae farms. The arid climate of the desert is very supportive of algae growth, and the nearby ocean could supply saltwater for the algae ponds. Enough biodiesel to replace all petroleum transportation fuels could be grown in 11,000 square miles, or roughly nine percent of the area of the Sonora desert.
The algae farms would not all need to be built in the same location, of course. In fact, it would be preferable to spread them around throughout the country, to lessen the cost and energy used in transporting the feedstocks. Algae farms could also be constructed to use waste streams (either human waste or animal waste from animal farms) as a food source, which would provide a beautiful way of spreading algae production around the country. The algae farms also yield recoverable methane (commonly referred to as "biomethane" when it comes from biomass). This methane could then be turned into methanol, to provide a biomass derived source of alcohol for turning the algal oils into biodiesel. The left-over sludge remaining makes an ideal fertilizer, high in nitrogen and phosphorous. Such algae farms could also use the waste-streams from agriculture to aid algae growth.
In "The Controlled Eutrophication process: Using Microalgae for CO2 Utilization and Agircultural Fertilizer Recycling"3, the authors estimated a cost per hectare of $40,000 for algal ponds. In their model, the algal ponds would be built around the Salton Sea (in the Sonora desert) feeding off of the agircultural waste streams that normally pollute the Salton Sea with over 10,000 tons of nitrogen and phosphate fertilizers each year. The estimate is based on fairly large scale ponds, 8 hectares in size each. To be conservative (since their estimate is fairly optimistic), we'll arbitrarily increase the cost per hectare by 50% as a margin of safety. That brings the cost per hectare to $60,000. Ponds equivalent to their design could be built around the country, using wastewater streams (human, animal, and agricultural) as feed sources. We found that at NREL's yield rates, 11,000 square miles (2.82 million hectares) of algae ponds would be needed to replace all petroleum transportation fuels with biodiesel. At the cost of $60,000 per hectare, that would work out to roughly $169 billion, to build the farms.
The operating costs (including power consumption, labor, chemicals, and fixed capital costs (taxes, maintenance, insurance, depreciation, and return on investment) worked out to $12,000 per hectare. That would equate to $33.8 billion per year for all the algae farms, to yield all the oil feedstock necessary for the entire country. Compare that to the more than $100 billion the US spends each year just on purchasing crude oil from foreign countries.
IV. Other issues
To make biodiesel, you need not only the vegetable oil, but an alcohol as well (either ethanol or methanol). The alcohol only constitutes about 20-25% of the volume of the biodiesel, so the volume of alcohol needed is only about 1/4 the volume of oil. One of the most land-efficient and energy-efficient way of producing methanol is using pyrolysis on biomass. One of the additional benefits of this method is that the process produces both methanol as well as charcoal, which can be burned for energy production (replacing coal, and producing no net CO2 emissions or sulfate emissions). In the early days of the automobile, most vehicles ran on biofuels, with Henry Ford himself being a big advocate of methanol produced from industrial hemp (not to be confused with marijuana, which is significantly different). The Department of Energy's "Mustard Project" has focused on the prospect of growing mustard for the dual purposes of biodiesel and organic pesticide production. Their process focused on alternating mustard crops with wheat. One nice effect of this is that the wheat could be used as the cellulose feedstock for producing alcohol through pyrolysis for biodiesel production.
V. Hydrogen?
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