.JPG)
Bio fuels compete 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 (C2H5OH), 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 (C19H34O2) 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 and oxygen and therefore the process is ' green.'
However, energy can be used in the production of these fuels so releasing more CO2. Rapeseed and maize produce up to 70% and 50% more greenhouse gas due to the level of nitrous oxide emissions (from fertilizers) which is 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 as follows:- (ref161):-
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Corn ethanol 78% (weight of CO2 per volume fuel) compared to gasoline.
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Cane ethanol 44% compared to gasoline.
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Cellulosic ethanol ( eg switchgrass, stalks, husks of corn, woodchips, sawdust, paperpulp) 9% compared to gasoline.
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Bio diesel (rapeseed oil, soya, peanut, sunflower, palmoil) 32% compared to diesel oil.
- Generation 2 bio. (Willow, grass, polar, eucalyptus); zero or negative (Ref 182).
- Algae, bugs and other new developments - figures to come.
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 no saving but a large increase in greenhouse gas.
Deforestation accounts for 20% of global greenhouse gas emissions. It takes 840 years for a palm oil plantation to soak up the carbon released when forest is burnt so where forest is destroyed to plant Palm oil for fuel the process is not sustainable. At present vast areas of rain forest are being destroyed.
Using ethanol boosted direct injection (EBDI) which achieves higher engine pressures, plus several other refinements, advantage is taken of the higher octane value and higher heat of vapourisation in ethanol, resulting in an engine with higher efficiency than a diesel. (ref 195)
Generation 2 bio.
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.)
Direct conversion cellulose ethanol is being researched by the University Wisconsin-Madison (Ref 182). Sustainable Bioenergy Centre UK (Cambridge, Dundee, York, Nottingham universities, Rothamsted Research) are researching the use of willow, straw which are sustainable as they can be grown on waste land without fertilizer. Sugars are extracted from the plant cell walls in a process using enzymes. These are broken down with yeast and bacteria to produce butanol and ethanol, transport fuels (ref 193).
Camelina (brassica family) seed is crushed to produce triglyceride and refined to synthetic kerosene for aircraft.
Jatropha, a low height shrub that can be grown in tropical and semi tropical climates on poor soil yields oil from the seed crop. It is claimed that the bush could supply 4 times more fuel per given area than soya or ten times as from a maize. The fuel has been used in a 50:50 mix with jet fuel in aircraft.
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) Lower need of landfill sites, 2) Use of methane. This would otherwise 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) Production of 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. 80,000 tons 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
Pig farm sewerage to heat and electricity.
Sansuy in conjunction with local farmers has been installing co- generation units in Argentina where liquid and solid pig sewerage is fed into a digester to produce methane used as fuel to heat pig sheds, soybean deactivation (fed to pigs) and to generate electricity for use on the farm. (ref200).
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. Explanation and illustration.
Ineos chemicals claim that they can make 400 litres (90 gallons) ethanol from one tonne of dry waste, heated to produce gas , feeding the gas to bacteria which produce ethanol which can then be purified.
TMO renewables (UK) plan to build first plant in 2010. The process uses much less energy than producing ethanol from corn. It uses a wide variety of marterial grown on land not otherwise used for farming or forest. TMO renewables
Diesel and jet fuel from algae - developments (ref214.)
Growing algae for fuel (see also ref 181).Exxon say that 2000 gallons per acre can be produced, 3X the area of biodiesel from palm oil and 8X the area for ethanol from corn. If cultivated in sewer and water treatment plants, chemicals such as phosphorous, nitrogen and CO2 can act as nutrients (to the algae).
Algae is grown in ponds or bioreactors where water with nutrients passes through tubes exposed to sun. Photosynthesis shown above. Oil can be squeezed out as above or chemically.
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. see algae house
The US has set a target of producing 36 billion gallons fuel by 2022; an increase from 11 billion gallons today.
Sunshine to Petrol / Gas.
Counter Rotating Ring Receiver Reactor Recuperator (CR5)
The Sandia National Laboratories are developing a process for converting CO2, captured from a power station or from the air, to produce methane. The CO2 is broken down to carbon monoxide and oxygen using heat from solar reflectors - (Concentrated Solar Power - CSP). Water can also broken down to hydrogen and oxygen. Carbon monoxide, hydrogen, and oxygen, ultimately could be used to synthesize liquid fuels in an integrated S2P system.
Artificial organisms - bacteria - biomass to hydrogen - development.
Artificial organisms are being developed to synthesize new species of bacteria that produce hydrogen as a fuel - Craig Venter Institute, Rockville. The university of Glamorgan UK is developing a plant to produce Hydrogen from biomass and bacteria.
