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Pongamia Biofuel Production

Fuel from vegetable-based oils is not a new idea. Rudolph Diesel demonstrated the first diesel engine that ran on peanut oil. He became something of an alternative energy evangelist and in 1912, a year before his death, Diesel predicted that vegetable oils would become as important a source of fuel as petroleum products.
[ see: How Rudolf Diesel's engine changed the world ]

Hawaii Pacific Energy Group's clean energy mission is to be a leader in producing bioenergy at a cost on par with conventional energy resources, on lands not suitable for food crops while ensuring social inclusion and long-term economic, sustainable activities that improve the environment as a secondary benefit. One means to accomplish this endeavour is by generating biofuels that can be used in place of conventional fossil fuels. We are developing the production of biofuels derived from the Pongomia tree that can be used in place of conventional petroleum-based diesel.

Millettia pinnata, or Pongamia, is a tree that originally natively grows along rocky and sandy shores and in mangrove forests. Its flowers are pink to white and quite fragrant. After pollination by insects, a pale brown fruit pod is formed. The seeds inside the pods contain pongamia oil that traditionally was used as an illuminant fuel in oil lamps, but after refinement into biodiesel it can be used in place of petroleum-based diesel.

Pongamia grove
A grove of Pongamia trees ( � NParks Flora & Fauna Web )

HPEG specializes in the advancement of the cultivation of elite Pongamia trees, which can be cultivated on unproductive wastelands, and using the trees' seed production to extract oil that can easily be converted to biodiesel. This creates productive assets that supply the perennial and inelastic energy market with both biodiesel and green coal, a by-product This high-value energy production adds to the local and national GDP, thereby reducing foreign energy imports while adding value to all levels of the energy supply chain.

Pongamia influorescence
Pongamia influorescence
Pongamia flowers
Fragrant Pongamia blooms

Pongamia oil comes from pressing the seeds of the Pongamia tree, which are about 35% oil. The crude Pongamia oil could be combusted directly, but typically engine manufacturers demand that the oil be further processed into biodiesel. Unlike other biofuels, Pongamia biodiesel has a much higher energy density than the energy input required to produce the oil. One study has the energy output:input ratio at 20:1 for Pongamia biodiesel.

Pongamia seeds
Pongamia seeds. (a) immature seed (b) juvenile seed (c) mature, oil-laden seed

Pongamia biodiesel is a high-quality biodiesel with calorific values, cloud points, and flash points favorably comparable to petroleum-based diesel.

See: Fuel Laboratory: Quality of Crude Pongamia Oil Report

Hawaii Pacific Energy Group's Pongamia biodiesel value rating

With its partner, HPEG has developed a very high pongamia biodiesel value rating, particularly with respect to meeting Hawaii's environmental sustainability challenges. Energy and related carbon emissions are one example of the environmental challenges facing Hawaii. Other related challenges include degradation of ocean ecosystems, concerns about reliable fresh water supply and how to manage solid wastes in a geographically constrained space.

Challenges & Opportunities

Hawaii has the highest energy costs for electricity and transportation in the USA and has among the highest overall electricity costs in the world for island communities because a significant part of the state's electricity generation is through the use of fossil fuels.

Hawaii has challenging and long-term unsustainable social, economic, and labor issues, particularly as the agriculture industry is in a transition.

HPEG's objective is to become a knowledge and application center for renewable energies.

HPEG offers a large and unique opportunity for Hawaii and other island communities: addressing the state’s 70% renewable energy target by converting agricultural land that is no longer in use into bioenergy plantations; using a proven technology to provide clean energy; and creating thousands of jobs for the local economy.

Hawaii Pacific Energy Group's Solution

HPEG's solution is to introduce elite Pongamia trees and non-edible vegetable oils at a large scale from which to produce biodiesel. Pongamia has already been introduced to Hawaii and is an ideal crop tree for marginal, semi-arid lands that are not suitable for conventional food crops while at the same time provides a proven renewable energy solution.

The key challenge for success in biofuels is providing a raw material that is scalable, does not compete with food crops for land and water resources, has production costs that are competitive to fossil fuels, and that has a high energy density.
Pongamia is a perennial legume crop that is a proprietary tree variety that cuts time to yield in half and quadruples the average yield per acre, has energy density ratios greater than 20 compared to less than 1 for corn-based ethanol, and that can be used to produce biodiesel with production costs under $0.39 per liter ($1.44/gallon, $43.30/barrel).

Production of Biodiesel from Pongamia-derived vegetable oil

Biodiesel is produced through a series of physical and chemical processing of the oil obtained from Pongamia seeds. The process of extracting crude oil from Pongamia usually involves only one or two simple mechanical operations whereas the process of extracting oil from coconut or palm may involve many steps. The two main processes for extracting oil from the seed feedstock are mechanical press extraction and solvent extraction.

In the mechanical press extraction, the oil seed feedstock is first heated to about 45�C. The oil seed is then crushed in a screw press. After most of the oil is removed, the remaining seed meal can be used as an animal feed or made into oil cakes that can be used for briquets. The solvent process extracts more of the oil contained in the oil seed feedstock, but requires more costly equipment. The process uses a solvent to dissolve the oil. After extraction, a distillation process separates the oil from the solvent. The solvent is condensed and can be recycled and reused in the process. Solvent extraction produces a vegetable oil with a higher degree of purity than the mechanical press process.

The central problem in using plant oil as diesel fuel is that plant oil is 11 to 17 times more viscous (thicker) than conventional diesel fuel. Plant oil also has very different chemical properties and combustion characteristics to those of conventional diesel fuel. If the fuel is too thick it will not atomize properly when the fuel injectors spray it into the combustion chamber of an engine and thus it will not combust properly – the injectors may get choked up, leading to poor performance, higher exhaust emissions and reduced engine life. 

The process of transesterification reduces the high viscosity of plant oil, resulting in a higher-quality fuel. In the transesterification process, the vegetable oil is reacted with alcohol (methanol or ethanol) in the presence of a catalyst (usually sodium hydroxide). The oil molecules (triglycerides) are broken apart and reformed into methyl esters and glycerin, which are then separated from each other and purified. Glycerin is a valuable by-product that can sold separately for many uses.

Biodiesel production

Biodiesel is a mixture of fatty acid alkyl esters. Esters are compounds of alcohol and organic acids. Fatty acid methyl ester is made by bonding methanol to the Pongamia oil. The process is relatively straightforward, but must consistently achieve prescribed standards to minimize the risk of damaging expensive diesel engines. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a petroleum diesel blend to reduce levels of particulates, carbon monoxide, hydrocarbons and air toxins from diesel-powered vehicles.
Resource balance
Pongamia biodiesel production resource and energy balance

Beaker of pongamia oil
Pongamia biodiesel
Biodiesel is oxygenated, thereby dramatically reduces air toxins, carbon monoxide, soot, small particles, and hydrocarbon emissions by 50% or more, reducing the cancer-risk contribution of diesel by up to 90% using pure biodiesel. Air quality benefits are roughly proportional to diesel/biodiesel mixtures. Biodiesel’s superior lubricity helps reduce engine wear, even as a small percentage additive. The most common use of biodiesel is as B20 (20% biodiesel, 80% diesel) and B2 (2% biodiesel, 98% diesel) or B1 (1% biodiesel, 99% diesel). The use of these blends requires no engine modifications. But because it gels at higher temperatures than petroleum-derived diesel, pure biodiesel requires special management in cold climates. Biodiesel contains slightly less energy than petroleum diesel, but it is denser, so that fuel economy tends to fall 7% for every 10% biodiesel in a fuel blend.
When applied in its pure form, biodiesel has a higher flash point than fossil-based diesels, and its viscosity results in a more intense pulverization, which is another disadvantage. Nevertheless, if properly treated, these shortfalls can be abated – and the advantages of biodiesel greatly make up for its disadvantages. It is non-hazardous, non-toxic and biodegradable. It reduces air pollutants such as particulates, carbon monoxide, volatile hydrocarbons and air toxins, thus significantly reducing impacts to climate change. It burns more efficiently than petroleum diesel, and its higher lubricity can reduce engine wear, prolonging the engine's lifetime.

Pongamia pilot project Pongamia pilot project
Pongamia pilot project on Oahu, Hawaii

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