Energy is considered the basis for the progress and prosperity of nations and societies. It is also the cornerstone of economic and social development. In many developing countries energy from biomass continues to be the main source of energy, mostly in its traditional forms designed to meet the demands of domestic use (Hall and Rosillo, 1998). In industrialized countries, the use of biomass for energy production has been increasingly proposed as a substitute for fossil fuels. The limited availability of fossil fuels and the growing awareness of the detrimental environmental consequences resulting from greenhouse gas emissions have reinforced the importance of biomass as an energy resource in developed and developing countries.

In Egypt, crop residues are considered to be the most important and traditional source of domestic fuel in rural areas. These crop residues are by-products of common crops such as cotton, wheat, maize and rice. The total amount of residues reaches about 16 million tons of dry matter per year. Cotton residues represent about 9% of the total amount of residues. These are materials comprising mainly cotton stalks, which present a disposal problem. The area of cotton crop cultivation accounts for about 5% of the cultivated area in Egypt (MALR, 2002).

The energy equivalence of these energetically usable residues of the main Egyptian crops is approximately 112 PJ/year. These residues can represent about 4.2 % of national primary energy resources. This means that these residues can be used as a source of renewable energy in rural areas, which may suffer from a lack of fossil energy.

Previously farmers used these residues as fuel resources for the traditional mud ovens in which their families cooked and baked. For this purpose, farmers stored these residues on the roofs of their houses or on the fields. This traditional way of handling these residues caused several problems because

• the residues formed a good habitat for insects, mice and snakes that developed in the pile,

• they promoted insect infestation by pests such as the pink bollworm, which reduces the quantity and the quality of cotton fibres,

• such storage increased the risk of destructive fire in the villages.

In accordance with Rule No. 1472 for the year 1994, as of 1999 the Egyptian Ministry of Agriculture obliged farmers to burn their cotton residues on the fields immediately after the harvest operation. The burning operation kills the insects and disease carriers that can develop in the residues and attack the nearby or following crops (MALR, 1996). This is, however, an environmentally unfriendly practice. It results in huge amounts of harmful gases and clouds of smoke covering the sky over Cairo and the surrounding regions. These emissions lead to environmental pollution and adverse effects for human health. As a result, also in the year 1999, the Ministry of the Environment applied law No. 4 for year 1994 which prevented the farmers from burning these residues on their fields (EEAA, 1994). Nowadays farmers are once again storing these residues or burning them illegally on the fields in the evening.

To solve this problem a new technology needs to be developed to handle these residues easily and safely, in particular to protect crops against the harmful disease carriers.

The objective of this study is to develop the fundamentals of a technology for energetic utilization of cotton stalks to reach the following targets:

• Solving the problem of harmful storing and burning of cotton stalks in Egypt and preventing the smoke clouds caused by this

• Handling of these residues via a phytosanitary method that is safe for both the environment and agriculture

• Producing a cheap, easily storable, and environmentally sound biofuel for rural areas in Egypt

• Contributing to job creation and rural development.

The key process of this technology is briquetting. During this process the harmful insects are hopefully killed and the huge volume of residues can be reduced to a practicable and easily storable form. Furthermore, the burning properties of the raw materials can be improved and the emissions caused during combustion reduced.

The technological, scientific and economic problems to be solved in order to reach these targets are how to process and press the cotton stalks, what temperature is needed to kill the cotton bollworms, and last but not least, what the costs of briquetting are. Since there is no experience of cotton stalk briquetting available and only little knowledge of briquetting similar materials, it was necessary to conduct our own investigations and experiments.

Therefore, within the framework of this research, the following tasks had to be performed:

• Determine the minimum pressure and the optimum moisture content for obtaining stable briquettes.

• Study the influence of the press diameter and particle size on the density and stability of briquettes.

• Determine the minimum temperature that kills the bollworms.

• Study the behaviour of the moisture content of cotton stalks in the field.

• Study the combustion behaviour of briquettes and measure the environment-relevant emission during combustion.

• Evaluate the costs of the briquettes compared with commercially available fuel.

Because of the limited availability of cotton stalks in Germany where the work was to be done, some experiments had to be conducted with comparable materials such as poplar, hemp and rye straw.