.JPG)
Bio fuels competes with forests and food crops for space.
The use of fuel obtained from plant life is referred to as Bio fuel (refs 119 & 132).
Ethanol, a substitute for petrol, is made from crops rich in sugar or starch such as wheat, wood pulp or sugar cane. It has a lower energy content than petrol (67%) but higher octane rating, so consumption is lower and performance higher.
Bio diesel is made from vegetable oils, obtained from oilseed rape, palm oil, or animal fats. Often it can be blended with conventional diesel oil. The fuel consumption -energy content 86% - is higher than diesel (refs 160 &161).
Although CO2 is emitted when Bio fuel is used, growing the crops again will recapture carbon by drawing down CO2 and reconverting it to carbon within the crops and oxygen and therefore the process is ' green.'
However, energy can be used in the production of these fuels so releasing more CO2, or in the fertilizers involved. It is claimed that Rapeseed and maize produce up to 70 and 50% more greenhouse gas due to the level of nitrous oxide emissions which are 296 times more potent as a greenhouse gas than CO2. Between 3 to 5% of the nitrogen in the fertilizer is converted and released as the gas.
The overall greenhouse gas emitted with bio fuels and its production is less than from fossil fuels (ref161) by the following amount:-
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Corn ethanol 22% (weight of CO2 per volume fuel) less than gasoline.
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Cane ethanol 56% less than gasoline.
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Cellulosic ethanol ( eg switchgrass, stalks, husks of corn, woodchips, sawdust, paperpulp) 91% less.
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Bio diesel (rapeseed oil vegetable oil and used cooking oils) 68% less than diesel.
- Direct conversion cellulose ethanol (University Wisconsin-Madison research); zero or negative. (Ref 182)
As crops require a large area of land, which becomes unavailable for forests and farming, the net figures above may in some cases result in a negative saving or none. Bio fuel processed from cellulose biomass - tall grasses, willow, poplar, eucalyptus - and municipal waste should have minimal impact on forests and farming and could play a part long term. (ref 178.)
Jatropha, a four foot (1 1/4 m)shrub that grows on waste lane yields oil from a fruit which it is claimed can be cheaper that cane ethanol.
Biomass description and options in detail
Description and argument that biomass is not sustainable
Electricity and heat generated from waste food.
Three problems are solved here; 1) lack of landfillsites, 2) conversion of methane that would be produced at landfill sites from waste food left to rot etc (methane is 20 times more potent than CO2 as a greenhouse gas) and 3) a bio fuel for generation of electricity and heat.
See Greenfinch anaerobic digester site
Currently 28 million tonnes of landfill waste are produced in the UK. Generation is projected to approach 450 MW by the end of 2009. 80,000t of waste should produce 6 to 9 MW electricity so the potential would be 2800MW generation from waste in the UK., ie 4.2% of electricity output. (ref 189)
Sewerage to bio fuel
Zero carbon Cellulose to Ethanol - development.
A direct process using suitable catalysts taking a few minutes is to rapidly heat and then cool biomass, the cellulose sources being switchgrass, poplar trees, wood chips, corn stover. The research is being undertaken at the university of Wisconsin-Madison. The liquid can be used as created or further treated. The process does not in principle require external energy and the surplus heat can generate electricity making it carbon zero. (ref 182.)
Petrol (gas) from genetically modified bugs - experimental.
The DNA of single cell organisms, a billionth the size of an ant - industrial yeast or E -coli, are genetically modified so that their excretion is almost pure petrol. The 'feedstock' to enable fermentation may be wheat straw, wood chip or other material that can break down into sugars. The process takes place in giant stainless steel tanks. 'LS9' in California suggest that the "Oil 2.0" produced will be Carbon Negative. A floor area of 40 sq foot produces one barrel a week. To produce 140 million barrels of fuel a week (US consumption) an area of 200 square miles would be required. If it works on a very large scale fuel could be produced in 3 to 5 years. Explanation and illustration.
Ineos chemicals claim that they can make 400 litres (90 gallons) ethanol from one tonne of dry waste, heating waste to produce gas , feeding the gas to bacteria which produce ethanol which can then be purified.
Diesel from algae - development.
100,000 gallons of diesel per acre per year could be produced from growing algae (ref 181). If cultivated in sewer and water treatment plants, chemicals such as phosphorous, nitrogen and CO2 can act as nutrients (to the algae).
Professor Watanabe (Tsukuba University Japan) is developing a system using Botryococcus braunii algae which given light and CO2 excrete a crude oil. Algae could produce 30 to 100 times the amount of oil compared to rapeseed. Times on line diesel from Algae.
Artificial organisms to hydrogen - experimental.
Artificial organisms are being developed to synthesise new species of bacteria that produce hydrogen as a fuel - Craig Venter Institute, Rockville, Maryland.