Gasification in-situ with energy production or pyrolysis of the above mentioned residues, under a non-oxidizing atmosphere for alternative fuels production could be a solution to the environmental problems that land filling or conventional combustion could create.

There is a lot of gasification bioler development work underway at present. The current work in one study focuses on combustion and pyrolysis of cotton gin residues in Greece, as an alternative way of energy production.

In one recent trial of gasification technology gasification boiler operation has been put on a sound thermodynamic footing by the development work now completed. It has also been shown that, apart from its deleterious impact on thermal efficiency, the presence of water in mechanically-dewatered fuel (containing ~ 32 wt% solids) does not lead to significant particle disintegration compared with dried fuel. Gas trials have been staged using partial oxidation in three stages before final combustion. Nox emisssion rate was very well reduced from several thousand ppm to 25 ppm. Gasification in this system takes place in a fluidized bed formed above the slag bath and constituted by the dried sewage sludge or waste materials, the solid fuel, the oxygen-containing gas and the gasification gas. The gas produced in the gasifier can be used for power generation or for this example, as a reducing gas for iron ore.

In another study gasification of wide range of coals will be tested including biomass. Technology development will be based on: lab-scale experimental research using different coals, computer process simulation, demo-scale testing, plant configuration analysis for stepwise approach in respect of CO2 removal, system optimisation for power and chemicals production.

Gasifiers or boilers for gasification can frequently handle high fouling fuels without excessive slagging/fouling due to the lower temperatures at which they can operate in comparison with direct combustion units. Waste fuel gasification is going to be important as the cost of the refined product rises. This generally involves heating fuel in a gasification boiler in an oxygen-starved environment to produce a medium or low calorific gas.

Gasification of sewage sludge for heat and power generation in combined heat and power (CHP) applications is an attractive concept that provides an environmentally acceptable, efficient, and economically viable means of generating energy from a waste disposal problem. The final solid residues are pathogen-free but may contain toxic elements such as barium, copper, mercury, lead, and zinc at levels that could make their disposal to landfills costly as well as environmentally unsound. This is a concern which still needs addressing, but overall the problems also exist for other fuels and processes to a greater degree.

Gasification boiler gas emissions (syngas) is cleaned and then burned in internal combustion engines for the generation of electricity and process heat.

Sewage sludge wastes can also be coprocessed with coal to yield gas and liquid fuels or chemical feedstocks. This can be achieved with a wide range of other fuels and the pecific approaches quoted by the experimenters include:

- straw;
- wood wastes;
- plastics wastes;
- liquefaction of paper and papermaking wastes;
- waste tyres;
- oils, greases, and other waste-derived oragnic liquids;
- loaded rotary hearth furnace cokes

A number of plant modifications were necessary to accommodate these widely physically different feedstocks.

The gasification boiler (gasifier) generates a nearly uniform reaction front propagating upwards at a velocity of 0.77-0.87m/h. With a temperature of the reaction front maintained at 950-1050 degrees C. The gasifier, which resembles a stainless steel rocket, converts the carbon in the straw into a mixture of carbon monoxide and hydrogen gases known as “Syngas”.

The advantage of a gasifier is that it allows more efficient use of the fuel’s energy content and more even, controllable heat.

Gasification boilers have been used in the medical sphere for some time. The gasifier's stainless steel inside, from Rivers Medical Products, heats to around 850 degrees Celsius. The gasifier also features a rapid mix multi-port feed injector and actively cooled walls.

Some gasification boiler features are claimed to result in lower capital cost, higher efficiency, greater durability, higher availability, ability to handle low rank coal/lignite and better carbon conversion all resulting in a lower cost of electricity in associated IGCC plants. One gasifier-based dyeing oven quoted on the web, is said to save nearly 45% of the cost of fuel if it replaces a conventional biomass-burning oven and the savings are as high as over 60% if it replaces an oven using petroleum fuels. These aspects we have been told have compelled the operators to switch over to petroleum fuels from biomass fuels. If this is correct and we have no reason to think otherwise gasification will soon really take-off in ters of plant sales and volume of material including sewage sludge utilized.