Agricultural Research Service scientists study peanuts as energy crop

At the Exposition Universelle of 1900 in Paris, Rudolf Diesel demonstrated his revolutionary engine by using pure peanut oil as fuel. The most efficient combustion engine was even explicitly designed to run on plant oil and not on petroleum. Back then, the German genius made the visionary remark that one day, when petroleum resources run out, all cars would use plant oils grown by farmers in a decentralised manner and to their great benefit (earlier post). To some, we may be closing in on that day. Will the humble peanut make Diesel's prediction a reality? If it is up to researchers in the US, the answer is yes.

Land-suitability for rainfed cropping of groundnut under high inputs. Source: FAO, Land and Water Development Division; land suitability database for 30 crops.

Groundnuts or peanuts (Arachis hypogaea L.), a nitrogen-fixing legume, are cultivated in over 100 countries in the global south (overview at the International Crops Research Institute for the Semi-Arid Tropics). A look at a world map showing the most suitable areas for growing the crop reveals that there are vast stretches of land on the globe where groundnuts can be grown in optimal conditions. Interestingly, these suitable areas are situated in countries that currently belong to the poorest of the world - most notably in the Sahel (map, click to enlarge). Earlier, we had an in-depth look into this potential (here). To summarize that overview, we list a quick scan of the available hectarage per country. Let us take America, where peanut-oil biodiesel is gradually getting off the ground (previous post), as a reference case: United States: 23.8 million hectares of 'very suitable' to 'moderately suitable' land, with an average potential yield of 1.57 tons/ha.

Compare this with a few selected poor countries of the Sahel (in fact countries in Eastern Africa have an even larger potential):

• Sudan: 65.2 million hectares of 'very suitable' to 'moderately suitable' land, with an average yield of 2.1 tons/ha.
• Central African Republic: 28.2 million hectares of 'very suitable' to 'moderately suitable' land, with an average yield of 2 tons/ha.
• Benin: 9.2 million hectares of 'very suitable' to 'moderately suitable' land, with an average yield of 2.7 tons/ha.
• Burkina Faso: 14.6 million hectares of 'very suitable' to 'moderately suitable' land, with an average yield of 2 tons/ha.
• Chad: 24.6 million hectares of 'very suitable' to 'moderately suitable' land, with an average yield of 2.1 tons/ha.
• Mali: 17.5 million hectares of 'very suitable' to 'moderately suitable' land, with an average yield of 1.8 tons/ha.

In short, there is enough non-forest land and technical potential to expand the cultivation of this biofuel feedstock which has many benefits over other energy crops grown in semi-arid regions (see below). Optimitistically, we foresee a day when poor countries in the developing world will supply specially designed groundnuts that do not compete with food, to local biorefineries and biofuel world markets. Scientists from the United States Department of Agriculture's Agricultural Research Service (ARS) are contributing to this future by researching economically feasible peanut varieties for that very purpose.

Agronomist Wilson Faircloth at the ARS National Peanut Research Laboratory at Dawson, Ga., and Daniel Geller, a collaborative engineer at the University of Georgia, are testing a peanut called Georganic. It's not suited to current commercial edible standards for peanuts, but is high in oil and has low production input costs:
energy :: sustainability :: biodiesel :: biomass :: bioenergy :: biofuels :: energy crop :: groundnuts :: peanuts :: Sahel :: plant breeding ::

Georganic — or similar varieties — will likely be the future of peanut biodiesel because it can be planted and grown with just one herbicide application for weed control, compared to the three to four applications typically sprayed during a growing season for edible peanuts. Additionally, these fuel peanuts are grown without fungicides, which are the greatest input cost in traditional peanut production.

To further reduce production costs and increase yield, the research team is also studying technology such as conservation tillage and selection of varieties with high tolerance to multiple diseases. Currently, there are 24 peanut varieties being scrutinized in this biodiesel screening project, including Georganic, which was developed by ARS breeders in Tifton, Ga. Promising varieties also include DP-1 and Georgia-04S, a new high-oleic-acid, Spanish-type peanut.

Many old and new peanut varieties are being tested for field performance, and their oils are being analyzed for diesel performance characteristics. It has been found that high-oleic-acid peanuts—a quality desired for extended shelf life of food products—also make the best biodiesel fuel.

Today, soybean oil is the primary oil used in the United States for biodiesel fuel production. Soybeans produce approximately 50 gallons of fuel per acre, while traditionally grown peanuts can produce approximately 120 to 130 gallons of biodiesel fuel per acre.

Groundnut is an interesting energy crop for several reasons:

• it grows well in semi-arid regions and requires limited fertilizer and water inputs
• therefor it does not cause any pressures on rainforest ecologies, a critique often raised against other tropical energy crops (most notably palm oil)
• the regions where groundnut thrives are populated by the world's poorest people (especially Sahelian countries, like Mali, Niger, Mauritania, Chad, the Central African Republic, Sudan -- who all rank at the bottom of the scale of, for example, the Human Development Index)
• many non-commercial and non-edible varieties with high yields can be developed and improved
• in contrast to other energy crops which thrive well in semi-arid regions, such as the perennial shrubs jatropha curcas and pongamia pinnata, groundnut can be harvested mechanically

All of the crop's parts can be used as bioenergy feedstocks:

• the nuts themselves have a high oil content (around 50%) and one hectare of groundnut yields around 1000 litres of oil; the oil has a relatively low melting point, a medium iodine value and a high flash-point - characteristics which make it a suitable oil for biodiesel production
• the groundnut has a residue-to-product ratio of around 0.5-1.2 for pods and 2.2-2.9 for straw; this means that for every ton of nuts produced, 500 to 1200kg of shells become available and 2.2 to 2.9 tons of straw residue are harvested; in total groundnut yields between 3.7 and 5.1 tons of biomass per hectare
• these residues offer an interesting solid biofuel, with a relatively high energy content of 16Mj/kg for shells and 18Mj/kg for straw - with advanced bioconversion technologies (cellulosic ethanol or pyrolisis) this 'waste' biomass can be turned into liquid fuels and bioproducts; alternatively, it could be densified and used in biomass (co-firing) power plants

References:
USDA ARS: Peanuts Studied as Source of Biodiesel Fuel - July 30, 2007

Biopact: US firm Perihelion to use peanuts for biodiesel - January 30, 2007

Biopact: The spirit of Rudolf Diesel: peanuts and socialism - September 19, 2006

International Crops Research Institute for the Semi-Arid Tropics: Groundnut (peanut), profile.