|Low Cost Charcoal Gasifiers for Rural Energy Supply (GTZ, 1994, 49 p.)|
|10. Concepts of future dissemination of small gasifier-engine systems|
Not every detail of the gasifier technology has yet been solved, and the rather convincing approach of the ferrocement gasifier as a cheap and reliable equipment in the power range of around 1 0 kW is just a first step. But, if the advantages of big-energy in a future energy supply scenario are taken seriously, it just depends on the decision to do it.
This decision has to be based on a broad public support. Gasification technologies are rather unknown, compared to other renewable energies like photovoltaics, wind energy, and even biogas plants. Quite a lot of prejudices and misinterpretations appear when people are confronted with a technology which is based on biomass consumption- that is, at least in industrialized countries closely connected with overexploitation of forest reserves, which is definitely not the meaning of "sustainable biomass manage meet". A correct and comprehensive information about the meaning of "energetic use of biomass" in the context of a sustainable biomass management is necessary to create a general acceptance.
A new technology - and for the user, a gasifier is a new technology - needs some support to be integrated in a commercially oriented economy. Even under the improved starting conditions which an economically viable ferrocement gasifier may have compared to its more expensive predecessors, this technology will have to compete with more familiar and established equipment and even face an unfair competition with subsidized prices for liquid fuels.
Any dissemination of gasifier technology must therefore be based on an energy policy which encourages the use of new and renewable energies. India and Thailand belong to the few countries which already go in this direction:
"The Thai government has adopted a policy of utilizing locally available energy sources in order to reduce the amounts of imported energy. (...) For biomass this policy calls for a more efficient utilization of wood and charcoal and using more crop residues such as rice husk and bagasse".
The Thai government encourages the adoption of nonconventional energy technologies through soft loans and tax exemptions for manufacturers of technically reliable gasification systems. An important demand is seen in rural electrification: 6% of the 50000 villages of Thailand are not connected to the grid, but is is estimated that 20 % of the rural population needs decentralized energy supply due to the fact that even existing electric grids can not supply all households and the numerous demands in the fields (e.g. irrigation pumps). Furthermore, mechanical energy is needed for rice milling, paddy threshing, milling of corn, cutting of wood in sawmills, crushing and squeezing of sugar cane .
The most important power demand is seen in the range of 5-10 kW.
According to Jain , the situation in India is very similar: "Changes in international oil scenario and increased import budgets for petroleum products etc. resulted in specific commitment being made to renewable sources at the national policy making level. This has been reflected through establishment of a separate department (Department of Nonconventional Energy Sources - DNES) within the Ministry of Energy at the Government of India level and establishment of state nodal agencies to propagate increased use of renewable sources in almost all states".
In the context of an overall national strategy aimed at reducing dependence on imports of petroleum products, power generation by gasifier systems is seen as a major focus. A need is defined for mechanical shaft power applications with major emphasis on irrigation systems, on electricity generation for rural industries, farms and institutions, and in direct heat applications for rural industries as well as for institutional cooking. The relevant power range, especially for millions (!) of irrigation water pumps, is 3.5-7.5 kW. For rural electrification and thermal applications, 10 kW electrical output respectively 50 kW thermal output is the adequate size.
Jain gives an interesting assessment of the quantitative impact of a large scale application of gasifier units for irrigation pumping in India:
- 1% of the current national firewood consumption can be adequate for producer gas based operation of 240000 pump sets (3.5 kW each) or for electrification of 60 000 villages.
- A farmer could just use 3 to 4 % of his land for fast growing tree species to support his entire irrigation needs perennially. Alternatively, he could use up to 25% of the residues produced and meet his irrigation needs through small scale producer gas systems.
- Typical energy plantation yields can be anywhere between 10 tons and 60 tons (wet weight) per hectare and year and the country has a minimum of 62 million hectar of wasteland, a significant fraction of which could be used for energy plantations."
According to Jain, even hundreds of thousands of small scale gasifier systems would only have a marginal impact on the environmental balance. Nevertheless, it is desirable to focus dissemination programmes on biomass surplus areas and to ensure the sustainable production of feedstock, either in terms of residues or through fast growing tree species.
It must be seen, however, that despite all governmental support the dissemination of gasifier technologies in Thailand and India has not yet been as successful as expected. Obviously, the gasifier technology is still not as attractive to the potential user, compared to the conventional diesel or gasoline system.
Stimulating large scale applications of gasifier systems
The next steps should be the integration of demonstrative plants in project activities which present a convincing model for"biomass management". Having in mind that gasifier technology can contribute to environmental protection, especially with respect to the global concern about CO2 emissions, some isolated demonstration projects are definitively not enough. A large scale application however will depend on politic decisions and economic considerations and will require the following steps to be taken:
(1) Effective use of biomass resources for energetic purposes has to be recognized as part of a policy of increased use of regenerative energies with the aim to reduce expenses for petroleum products, to reduce CO2 emissions and to increase the living standard in underprivileged areas. Biomass energy has to be considered as an important contribution to the efficient and sustainable management of biomass resources.
(2) Local manufacturing of gasifier systems should be encouraged by investment subsidies and tax exemptions.
(3) The energy demand and the respective demand and offer of biomass fuels has to be balanced. This will require careful selection of sites for installation in the early phase of a dissemination programme. In the long run, a commercialization of gasifier fuels by fabrication of biocoal briquettes from agricultural residues is one of the most important requirements for large scale introduction.
(4) With respect to application, two different strategies should be pursued:
a) Commercial application for irrigation water pumping, mechanical and electric power generation for cottage industries, gas generation for institutional cooking. A financial package of soft loans, tax reduction etc. may be necessary to compensate competitive advantages of traditional energy supply systems.
b) For underprivileged areas and communities, fully subsidized electricity supply can be seen as a part of a policy of compensation of social deficits. The involvement of gasification technology offers a step to rural autonomy and creation of additional jobs on the countryside. A continuous technical assistance will be necessary until the technological knowledge and experience has settled. Energy provision alone, however, will not be sufficient for any progress.
(5) The aspect of fuel supply for gasifiers should be seen in a context with the fuel supply for cooking purposes. In the long run, firewood and charcoal from forest reserves should, to a large extent be replaced by fuels derived from agricultural and forestry residues. The cultivation of fast growing energy plants on areas, not needed for agriculture, may be a necessary contribution to the energy potential.