International discussion forum on landfill gas - Information and advice

<BODY> <br><h1></h1><br> <br><h2>Landfill gas production in brief</h2><br> All common landfill sites receive varying amounts of combustible organic waste. Under anaerobic conditions, this organic waste will be converted to methane (CH4) by quite complex microbiological processes. The rate at which this decomposition takes place depends primarily on the following three conditions: 1. The nature of the waste; a log will take decades to decompose while fatty waste decomposes fairly quickly. 2. The biological processes are very temperature-dependent; the higher the temperature, the faster the process will be. 3. The waste must be moist for the biological processes to take place; dry waste will not decompose. Gas production is normally halved after an average of 15 years. The gas contains varying concentrations of methane – a combustible and explosive gas. It also contains carbon dioxide and nitrogen that are neutral in terms of energy. Methane is a strong contributor to the enhanced greenhouse effect. The energy from the landfill gas can instead be utilised in a gas boiler or a gas engine driving an electricity generator to produce heat or combined heat and power. The recovery of landfill gas therefore serves a dual purpose: 1) it reduces the greenhouse effect, and 2) it saves on other fuels. The gas can be recovered by the installation of vertical boreholes containing perforated suction pipes or by means of vertical fascines in the waste (a sort of drain line). By applying suction at the gas boiler or gas engine, the pressure in the landfill site is lowered, and the gas will migrate towards the boreholes or fascines from where it is conducted through gas pipes and can be recovered. As the pressure difference is only a few millibars, high and low pressure weather conditions will greatly affect the daily gas recovery rate. Since 1996, an EU directive has banned landfilling of combustible material in EU countries. Landfill gas recovery is therefore in strong decline in these countries. <br><h2>international discussion forum on landfill gas</h2><br> <br><h2>Contact us at:</h2><br> Viboregnens Energi- og Miljøkontor % Naturgas Midt Nord Vognmagervej 14, 8800 Viborg Tlf. +45 8661 2322. Fax. +45 8661 4146 viborg@sek.dk <br> <p><a href="http://www.biogasinfo.org/energy02/html/kontor_fr.html">om kontoret</a></p> <p><a href="http://www.biogasinfo.org/energy02/html/biogas_dk_fr.html">Biogas i Danmark</a></p> <p><a href="http://www.biogasinfo.org/energy02/html/biogas_uk_fr.html">Biogas in english</a></p> <p><a href="http://www.biogasinfo.org/energy02/html/losseplads_fr.html">lodsepladsgas</a></p> <p><a href="http://www.biogasinfo.org/energy02/html/gaard_fr.html">Gårdbiogas</a></p> <p><a href="http://www.biogasinfo.org/energy02/html/farm_fr.html">farm scale biogas </a></p> </body>