biomass briquetting in sudan: a feasibility study
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BIOMASS BRIQUETTING IN SUDAN:
A FEASIBILITY STUDY
This publication was produced for the United States Agency for International Development. It was prepared by Dr. Ahmed Hassan Hood under the direction of the Womens Refugee Commission.
Executive Summary Generally, biomass can be defined as renewable organic materials that contains energy in a chemical form that can be converted to fuel. It includes the residues from agricultural operations, food processing, forest residues, municipal solid wastes and energy plantations. The use of biomass residues and wastes (for chemical and energy production) was first seriously investigated during the oil embargo of the 1970s. In recent years the use of biomass as a source of energy became of great interest world-wide because of its environmental advantages. The use of biomass for energy production, biofuels, has been increasingly proposed as a substitute for fossil fuels. Biomass can also offer an immediate solution for the reduction of the CO2 content in the atmosphere. It has three other main advantages: firstly its availability can be nearly unlimited, secondly it is locally produced and thirdly the fact that it can be used essentially without damage to the environment. In addition to its positive global effect by comparison with other sources of energy, it presents no risk of major accidents, as nuclear and oil energy do. Due to their heterogeneous nature, biomass materials possess inherently low bulk densities, and thus, it is difficult to efficiently handle large quantities of most feed stocks. Therefore, large expenses are incurred during material handling (transportation, storage, etc.). Very often, of all the factors considered, transportation presents the second highest cost, next to capital recovery. It was also noted that transportation costs of field residues will increase with the increasing size of a conversion facility. In order to combat the negative handling aspects of bulk biomass, densification is often required. The process of compaction of residues into a product of higher bulk density than the original raw material is known as densification or briquetting. Densification has aroused a great deal of interest in developing countries all over the world in recent years as a technique of beneficiation of residues for utilization as energy source. The advantages and benefits of biomass densification are:
- It improves the handling characteristics, reduces transportation cost, enhances its volumetric calorific value, and produces a uniform, clean, stable fuel, or an input for further refining processes. Although briquetting of biomass does not add to its heat value, briquettes are easier to transport and store. Briquettes are six to ten times denser than loose biomass, burn more efficiently, and create less pollution.
- Normally the bulk density of loose biomass is in the range of 0.05-0.02 g/cm3 and can be densified to briquettes of density 1.1-1.4 g/cm3. Densifying biomass feed stocks improves the process of feeding the fuel into co-fired power plants (e.g. coal). Also, the combustion of dense granulated and uniformly sized biomass can be controlled more precisely than loose, low bulk density biomass and thus reduce emissions.
- Biomass briquetting provides additional income to farmers, creates jobs and possibly rural development - it can serve social and economic functions as well.
Biomass densification represents a set of technologies (ranging from very simple to very complex) for the conversion of biomass residues into a convenient fuel. The technology is also known as briquetting or agglomeration. Depending on the types of equipment used, it could be categorized into five main types:
- Piston press densification
- Screw press densification - Roll press densification - Pelletizing - Low pressure or manual presses
Early introduction of biomass densification in Asia, particularly India and Thailand, was primarily through private sector endeavors. Such ventures showed limited success because of:
- Mismatch of technology, raw material supply and prospective markets, - Technical difficulties and the lack of knowledge to adapt the technology to suit local
conditions, - Excessive operating costs (mainly electricity and maintenance), - Lack of focal points for the accumulation and exchange of experiences in briquette
production in conjunction with advances in briquetting technology.
Collaboration, coordination, joint research, involvement of the private sector and donor support resulted in overcoming the constraints and barriers. The design and manufacture of briquetting machines appears to have evolved and been adapted to suit local conditions in different countries. India and China take the lead in the manufacture of briquetting equipment, particularly the ram and die technology. It was also realized, at early stages, that briquettes are best suited as an industrial fuel. The marketing constraints were addressed through directing briquettes to industrial and institutional uses as substitute for solid industrial fuels, particularly coal. The use of briquettes in the domestic sector proved unrealistic due to the relatively low price of fuelwood and the need for specially designed stoves for briquettes. The two common types of briquetting presses employed in Asia are heated-die screw press and piston press. It appears that heated-die screw press technology is preferred in most East and Southeast Asian countries while the piston press is dominant in India. The most common raw materials used in biomass densification in Asia are: sawdust, rice husk, coffee husk, tamarind seeds, tobacco stems, coir pith and spice waste. However, successful endeavors, mainly using heated-die screw, were obtained using sawdust and rice husk. Sawdust is practically the only raw material used for producing briquettes, which are subsequently carbonized; it is the dominant raw material in Malaysia, Philippines, Thailand and Korea. On the other hand rice husk is the only raw material used in Bangladesh. Apart from Bangladesh and Thailand, the use of biomass briquettes as domestic cooking fuel is rather limited in Asia. The main end use of biomass briquettes, particularly in India, is for industrial applications industrial process heat generation and institutional kitchens, where the fuel has a competitive price with coal. The government environmental policy to reduce coal utilization, regulations and incentives are the main deriving vectors for widespread use of biomass briquettes in India. Many biomass briquetting factories are funded through the Clean Development Mechanism, CDM. In Bangladesh, rice husk briquettes are used as domestic cooking fuel as well as in restaurants. The use of briquettes in humanitarian settings is only reported in Thailand, where the Government banned refugees' access to forests surrounding the camps. The briquetting industry flourished due to contracts for supply of briquettes to refugee camps. The history of biomass briquetting in Africa dates back to late 1970s and early 1980s, when it was realized that high dependence on fuelwood for domestic consumption was the main contributory factor to deforestation and desertification. Policy decisions were the driving forces
behind the push, and biomass briquettes were mainly intended for domestic consumption as substitute for firewood and charcoal. The raw materials most commonly briquetted in Africa are coffee husks and groundnut shells; sawdust and cotton stalks are also used to a limited extent. Unlike in Asia, the feature of briquetting programs in Africa was largely one of single projects in various countries which have usually not been successful. Unlike India and Thailand, no African country has developed anything resembling a briquetting industry with several plants based upon the same technology. In addition there was and is still no collaboration or coordination in Africa on research and development and other issues pertaining to the development of a briquetting industry. Although briquetting projects in Africa received high donor funding and policy support, four reasons seem to explain the failure of briquetting projects in Africa:
- Inappropriate or miss-specified expensive machinery was ordered - Poor planning in re: availability and supply of raw materials free supply of raw
materials was assumed - The low local prices of firewood and charcoal inhibited the marketing of briquettes - Poor marketing there is a clear failure to market the briquettes in the domestic sector.
Other existing markets do exists, but were not sufficiently considered - Little involvement of the private sector - High expectations, short project life spans and early withdrawal of donor as well as
government financial support In recent years, the introduction of small-scale low pressure briquetting is spreading in Africa, particularly in East Africa. However, the level of production is so low that anticipated impacts are negligible. In Sudan, biomass briquetting witnessed a boom during 1980s and early 1990s. The domestic sector the largest consumer of fuelwood - was the targeted end user of biomass briquettes. The main objective was to stem environmental degradation (desertification) caused by deforestation. Briquettes were manufactured using agricultural wastes such cotton stalks, groundnut shells and bagasse. Similar to the situation in other African countries, t