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Organic Waste to Energy: The Technology Today for Tomorrow

• In a global context, the major and minor players of the world are now looking seriously at renewable, sustainable and alternative energies, as a means to protect our fragile environment and natural resources.

• Seeking new technology and adapting present ones to produce energy, in a sustainable manner, has become a priority for MPCEE.

A major part of our activity is devoted to waste and resource management.

Producing Energy from Organic Wastes

MPCEE is pleased to introduce you to new technology for the continuous processing of organic waste materials into saleable products, including methane gas (the main constituent of natural gas) and high quality liquid and solid fertilizers.

By safely processing organic waste material, much of which can be toxic, and capturing the resulting methane gas for use as a fuel or heat source, the system makes a significant contribution to the improvement of the natural environment and the reduction of greenhouse gas emissions. The ‘bio-methane’ produced can be used as a vehicle fuel that creates virtually no toxic emissions, thereby enhancing the urban environment when compared with conventional fuels.

This system is unlike other organic waste digestion systems in that it is not a batch process but a continuous process allowing continuous intake of feedstock and continuous removal of output products thereby reducing the requirement for waste and product storage.

An even more significant advantage of this system is that the processing speed can be constantly and automatically adjusted to ensure complete digestion of the waste material that passes through it, thereby ensuring that the output products are clean and free of toxic or undigested waste. Heavy metals can also be separated out during the digestion process and collected for sale or safe disposal. Batch processors cannot compare with this system in either of these features.

This offers not only environmental benefits but sound investment potential also. Low construction and operating costs give potential for a high return on investment from the sale of the output products and from the collection of ‘gate fees’ for the receiving of waste materials.

This system has been developed by a British engineer who was also the person involved with Porsche sports car racing and who developed the technology that first allowed high performance car engines to run on lead-free petrol, which is now the acceptable fuel for use in every petrol engined car built in the world today.

There is global confidence that bio-methane, produced using this organic waste digestion system, will become the automotive fuel of the 21^st century.

The Advantages

This is the world’s most efficient and cost-effective technology for the treatment of organic waste. Its advantages are manifold and are summarized as follows:

Ø Low Environmental Impact:

ü The digester tanks are manufactured from low energy non-degrading materials such as polypropylene or high density polyethylene.

ü Tanks are immersed in heat-insulated lagoons that create low physical and visual impact on the local environment.

Ø Low Operating Costs:

ü The system operates at near ambient temperatures in tropical countries. Where local climatic conditions require supplementary heating of lagoons, heat is supplied either by solar-cells or from the cooling system of electrical generators powered by self-generated bio-methane.

ü It is fully automated using sophisticated system of monitoring and control equipment; hence labour requirements are very low.

Ø Digests Toxic Wastes:

ü Will digest organic wastes that are highly toxic if released into the natural environment – e.g. lactose waste from dairy processing is highly toxic to river systems.

ü Will cope with even highly toxic inorganic material such as household bleach and disinfectant if these are accidentally added with the feedstock to the digesters, though they will severely slow down the process as the digestive bacteria take time to recover.

ü Can be used to separate out heavy metals that are present in the waste material, and allow them to be collected for sale or safe disposal.

Ø Reduces Greenhouse Gas Emissions:

ü Relies on the recycling of organic (i.e. carbon-based) wastes. Fuels and fertilizers produced are therefore carbon-neutral; the carbon released by their being recycled from the atmosphere and released is not from fossil sources.

ü Captures methane that might otherwise be released to atmosphere. Methane that is released from the natural decay of organic material or from the breakdown of organic waste buried in refuse tips is 21 times more harmful as a greenhouse gas than carbon dioxide. This system therefore offers an excellent means of reducing greenhouse gas emissions by capturing methane, which can be used as a fuel for heating or transport to give a positive environmental effect.

Opportunities in Waste to Energy Applications

ü Reduction in Pollution and Greenhouse Emissions: Provides a cost-effective means of reducing pollution - in particular the ground water pollution resulting from buried organic wastes. In addition, methane gas that is captured and burned as a fuel provides a major reduction in greenhouse gas emissions (see above).

ü Low Cost Carbon-neutral Transport or Heating Fuel: The high purity methane gas produced is the main constituent of Natural Gas. It can therefore be used as a clean-burning carbon-neutral fuel for transport and heating, as a substitute for natural gas.

ü Cheap and Safe Fertilizer: High purity liquid and dry fertilizers are produced that can be applied directly to crops without risk of disease or pollution from run-off.

ü Taking a lead in the Environmental Field: This is 21^st Century technology that has recently been developed in England. The technology is protected by worldwide patents and license options have been purchased for use of the technology in several countries including the USA and Canada.

The Technology

Anaerobic digestion of organic waste is not a new technology. It has been used in China for over two hundred years and is still commonly used in rural communities for producing methane for cooking and lighting. This system differs from all other waste digestion systems in the patented design of its digestion tanks which allow the adoption of a continuous “first-in first-out” processing stream that results in very high purity of the digestion system outputs.

The Outputs

The outputs are the same as those produced from the natural degradation of organic waste. However this system is unique in ensuring a more thorough and complete digestion of waste products that can be separated into clean individual products as required. No other waste digestion system provides the “first-in first-out” flow pattern or the rigid control of the digestion process that achieves the purity of its outputs.

Marketable outputs from this anaerobic digestion system include:

ü High purity methane gas suitable as a vehicle fuel or as a substitute for natural gas

ü High purity CO₂ gas suitable for use in the soft-drink industry

ü High purity liquid fertilizer

ü High purity solid fertilizer

ü Process water for re-use

Martin Parr