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This page currently need further attention. It should also include some of the pros and cons of biofuels for household use in developing countries, present the issues from a more neutral point of view. If you have the necessary expertise we would greatly appreciate improvements on this page.
biofuels can be used to produce heat, electricity, and fuel for transportation. Currently most important biofuels are pure plant oil (PPO), bioethanol, and biodiesel, that are capable to conventional gears. Liquid biofuels are disposed in 1. and 2. generation fuels. PPO, Bioethanol and Biodiesel belong to 1. generation that can be produced by conventional technology. Synthetic biofuels (e.g. BtL Biomass to liquid) and ethanol from cellulose belong to 2. generation. In this case the total biomass (plant, residues etc) is used and transformed to fuel by a highly developed technology.
In the household energy context, liquid biofuels can be used to power farm equipment, to run small generators for individual households or minigrids, and as cooking fuels.
Newly cellulose is used to produce bioethanol. Cellulose is split by a hydrolysis of enzyms. After the split it is fermented and destilled like sugar (e.g. synfuel of IOGEN in Canada). In case of the production of «Biomass to Liquid» (BtL) total biomass is gasfied (thermochemical).
Fast pyrolysis refers to the rapid heating of biomass (including forest residue such as bark, sawdust and shavings; and agricultural waste such as wheat straw and bagasse) in the absence of oxygen.
There are many approaches, including bubbling fluidized bed reactors and rotating kilns. Three products are produced: biooil (60-75% by weight), char (15-25% wt.) and non-condensable gases (10-20% wt.). Yields vary depending on the feedstock composition. Bio oil and char are commercial products and non-condensable gases are recycled and supply a major part of the energy required by the process.
Feedstocks for biofuels with the greatest potential to displace imported petroleum are in the form of cellulosic biomass, including residues from agriculture and forest operations, urban woody waste, and energy crops such as hybrid poplar, hybrid willow and switchgrass,jatropa . Biofuels may be derived from woody biomass.
Ethanol can be produced from woody biomass, as it can from corn. However, there are several important differences between cellulosic ethanol and corn-starch ethanol. The sugars derived from woody biomass are a mixture of 5- and 6-carbon sugars, and as a result, fermentation organisms and processing conditions are more challenging than for corn ethanol.
Research continues to improve the enzymes and microorganisms needed to boost sugar and ethanol yields from woody biomass and to reduce costs of production. A fraction of the woody biomass known as lignin, which is not converted to sugars, is dried and burned to produce heat and power for the conversion process. This eliminates the need for fossil energy resources for the conversion steps to ethanol. As a result, the life-cycle reduction of fossil energy and greenhouse gas from cellulosic ethanol compared to petroleum gasoline on an equivalent energy basis is much improved compared to fossil gasoline and corn ethanol.
Thus far biofuels other than ethanol have not been discussed . Woody biomass can also be converted to a true hydrocarbon fuel (no oxygen in the fuel) that is nearly identical at a molecular level to petroleum liquid fuels, using thermochemical conversion steps: gasification and pyrolysis. Gasification converts the solid biomass into a synthesis gas comprised mostly of CO and H2. Pyrolysis converts solid biomass into an oily substance. In either case, these components are catalytically converted to hydrocarbon fuels called synthesis gasoline and synthesis diesel (syngas and syndiesel).
By adjusting reaction conditions, other fuels like jet fuel can also be produced. The obvious advantage of producing these synfuels is that their compatibility with existing vehicular transportation infrastructure is almost perfect, requiring very little if any modification. Studies have shown that the life-cycle, fossil energy, and greenhouse gas reduction of woody biomass-based synfuels compared to petroleum gasoline on an equivalent energy basis also is much improved compared to fossil gasoline and corn ethanol.
Biofuels are not a total solution to the issues of energy security or greenhouse gas reduction, but significant benefits are expected in the near future, at the same time that technology continues to advance in other sustainable energy technologies like solar power, hydrogen fuels, carbon capture and sequestration, etc.
- Winrock Nepal has conducted a country study for Nepal under the title 'Promotion of Biofuels for Sustainable Development in South and Southeast Asia (ProBIOS)' along with other south asian and southeast asian countries. The final reports are yet to appear on the website (http://probios.org/) but some of the conference proceedings will be useful.
- http://lecourrier.vnagency.com.vn/default.asp?CATEGORY_ID=16&NEWSPAPER_ID=40&TOPIC_ID=52&REPL Y_ID=37113
- Jatropha in Africa "FIGHTING THE DESERT & CREATING WEALTH"
- Biodiesel could fuel rural economic revival - By Sholain Govender
- Brazil. Bio-Diesel As A Rural Development Strategy
- India Planning Commission - http://planningcommission.nic.in/reports/genrep/cmtt_bio.pdf
- UNEP warns of dangers
- This important issue was covered in some depth by several speakers at the recent UK Soil Association conference - you can get transcripts and audio recordings here: http://www.soilassociation.org/conference. In particular, have a look at what was said by Jonathon Porritt, Richard Heinberg and Peter Melchett