Unconventional Green Fuels
Green fuels of the third generation are being developed from algae. Algae are simple organisms that range from the unicellular to the multi cellular forms. In their largest form they make up the genus of seaweeds. They are not considered as plants. They are prominent in bodies of water and form a base of food for other organisms that live in water. The advantage of algae is that it does not require land as a resource nor fresh water and can even use waste water. The cost of algae production and its harvesting is high but it is estimated that the energy yield per acre compared to other bio fuel crops that produce ethanol is almost thirty times. It is estimated that an acre of algae can produce up to 20000 gallons of bio fuel. The oil content of algae is almost 60 % of the weight and its conversion into a biodiesel is quite easy.
Catalysts are being used to convert biomass which is essentially waste from agricultural products, into alternative bio fuels. The object of this research into green fuels is to produce oils or fuels that very closely resemble gasoline, thus allowing the present engines in use to be still viable and this resemblance to the original gasoline would also allow the entire infrastructure that helps the sale and distribution of gasoline to be also used, without any additional expenditure.
Another form of green fuel that is being developed is from lingo cellulose. This is the non edible part of biomass like leaves and stalks, switch grass, forest residue and other agricultural waste that at the moment is only considered for waste disposal. The idea is not to convert them into ethanol, but instead aim for making them directly into gasoline, diesel and even jet fuel. The process is started by adding a solid catalyst to an aqueous solution that contains the biomass and water. This causes the formation of an oil layer which can easily be removed and transported. These form the functional intermediates that are further process and converted to the required green fuel. The further process will enable these intermediates to be directly converted to the required gasoline, diesel or jet fuel.
Four million tons of olive stones are available each year after the processing of olives into oil and other products. These stones can be further converted to ethanol. The process is to pre treat the olives stones with high pressure hot water and then add enzymes which allow the plant matter to degrade and generate sugar. This is further fermented with yeasts to produce the required ethanol. A yield of 5.7 kg of ethanol has been obtained from a 100 kg of stones. Similar processes can also be adopted for all other agricultural wastes and a lot of green fuel can be produced which not strain lands resources like the production of corn for ethanol does and thus make ethanol a more acceptable alternate fuel.