Hawaii Pacific Energy Group's Biofuel Projects

Pongamia Biofuel/SAF Production

Fuel from vegetable-based oils is not a new idea. Rudolph Diesel demonstrated the first diesel engine, which ran on peanut oil. He became something of an alternative energy evangelist and in 1912, a year before his death and over a century ago, 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 traditional fossil fuel-based energy resources, on lands not suitable for food crops while aiming for social inclusion and long-term economic, sustainable activities that improve the enviroment 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 seeds that can be used in place of conventional petroleum-based diesel or as a sustainable aviation fuel (SAF).

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 oil that traditionally was used as an illuminant in oil lamps, but after refinement into biodiesel, it can be used in place of petroleum-based diesel or as sustainable aviation fuels.

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

We specialize in the advancement of the cultivation of elite Pongamia trees, which can also be cultivated on unproductive wastelands and mine tailings, and using the trees' seed production to extract oil that can easily be converted to biofuels. This creates productive assets that supply the perennial and inelastic energy market with both biodiesel, SAF, and green coal as a by-product. This high-value energy production adds to the GDP of the local community as well as at the national level, thereby reducing foreign or offshore energy imports while adding value to all levels of the energy supply chain.

Pongamia influorescence

Fragrant Pongamia blooms

Pongamia seeds typically have an oil content of 28-34% to 42% by weight, depending on the tree's age and processing methods. The oil is extracted by cold pressing the seeds or by solvent extraction of crushed and ground seeds. The latter process generates a high-protein meal that can be added to livestock feed to increase meat production.

The crude Pongamia oil could be burned directly, but typically engine manufacturers demand that the oil be further processed into biodiesel or, for jetfuel type aircraft, into SAF. The crude Pongamia oil is first converted into biodiesel or SAF through a transesterification process involving an alcohol (like methanol) and a catalyst such as NaOH. Using Pongamia biodiesel leads to lower emissions of hydrocarbon and carbon monoxide gases compared to traditional diesel. Unlike other biofuels, Pongamia biofuels have a much higher energy output than the energy input required to produce the fuels. One study has the energy output:input ratio of 20:1 for Pongamia biodiesel.

Pongamia biodiesel and SAF are high-quality biofuels with calorific values, cloud points, and flash points favorably comparable to diesel and very similar to conventional jet fuel, and which burn more cleanly and with reduced particulate matter from their combustion.

The total energy potential of Pongamia extends beyond just the oil. The entire biomass of the tree can be used to improve the overall energy balance. A 2014 study of Pongamia in Bangladesh estimated the total energy content per hectare per year as follows:

This indicates that over 70% of the potential energy from the plant comes from the biomass byproducts, such as the seed cake and pods. Using these co-products for energy generation, such as for electricity or heat, significantly increases the system's total energy output. At a sufficiently large Pongamia plantation, the biomass could be used as feedstock for HPEG's EnvirOcycler reduction-oxidizer waste-to-energy technology to generate electricity for use in the local project community. One GJ is roughly 278 kWhr, which is enough to power about 8 homes during one day and a 500 ha (1,235 acres) plantation can provide power to those 8 homes for about one year.

Together with its partners, HPEG has developed a very high Pongamia biofuel value rating, particularly with respect to meeting Hawaii's environmental sustainability challenges. Energy and related carbon emissions are examples of the energy and 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.

Given that it is an island territory very far away from the continental USA, Hawaii has the highest energy costs for electricity and transportation in the USA and among the highest overall in the world for island communities.

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 as well as a provider of renewable energies.

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

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

Biodiesel or sustainable aviation fuel (SAF) is produced through a series of physical and chemical processes applied to the oil-containing Pongamia seeds. The process of extracting the crude oil from Pongamia seeds usually involves only one or two fairly simple operations whereas the process of extracting oil from coconut may involve many steps. The two main processes for extracting oil from the seed feedstock are mechanical cold press extraction and solvent extraction.

In the mechanical press extraction, the oil seed feedstock 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 a high-protein 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-based oil with a higher degree of purity than the mechanical press process.

The central problem in using plant oils such as diesel or kerosene-like fuel is that plant oil is 11 to 17 times more viscous (thicker) than conventional fuels. Plant oils also have different chemical properties and combustion characteristics to those of conventional fuels. 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 become choked up, leading to poor performance, higher exhaust emissions, and reduced engine life.

The process of transesterification reduces the high viscosity of plant oils, 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. See uses for glycerin.

Biodiesel and SAF are 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.

When applied in its pure form, biodiesel or SAF has a higher flash point than fossil-based diesels and kersones, and its viscosity results in a more intense pulverization, which can be another disadvantage. Nevertheless, if properly treated, these shortfalls can be mitigated – 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 or kersosene, and its higher lubricity can reduce engine wear, prolonging the engine's lifetime.