Technical Report

Biogas Upgrading to Vehicle Fuel Standards and Grid Injection

2007

During anaerobic digestion, i.e. degradation in the absence of oxygen, organic material is decomposed by bacteria forming digestate, an excellent fertilizer, and biogas, a mixture of carbon dioxide and methane.Anaerobic digestion (AD) has been successfully applied in recycling of biowaste and agricultural wastes, industrial wastewater treatment, stabilisation of sewage sludge and landfill management.

Today, farm-based manure facilities are perhaps the most common use of ADtechnology. By the end of 2005 17 million family-sized low-technology digesters were used in China to provide biogas for cooking and lighting. There are now over 3500 farm-based digesters operating in Europe and North America. Thousands of digesters help to anaerobically stabilise and thicken sewage sludge before it is used on agricultural land, dried and incinerated or landfilled. More than 2 000 high-rate anaerobic digesters are operated world-wide to treat organic polluted process waste water from beverage, food, meat, pulp and paper and milk industries.

Gas recovery from landfills has become a standard technology in most of the industrialised countries for energy recovery, environmental and safety reasons. Increasingly the gas is used in combined heat and power (CHP) engines or as a supplement to natural gas.

There are more than 250 plants operating or under construction using the organic fraction of source separated municipal solid waste (MSW) to produce a high quality compost or mechanically separated MSW to stabilise the organic fraction before landfilling. The total installed capacity is close to ten million tonnes.

The product of anaerobic digestion is a gas containing primarily methane and carbon dioxide, commonly called biogas. In small-scale installations, worldwide, the gas is primarily utilised for lighting and cooking. In larger units the gas can be used for cogeneration (generation of heat and electricity),as vehicle fuel or as fuel in industrial processes. The total European biogas production was in 2004 estimated to 50 TWh. This was a 43% increase from 2002. More than 55% of the biogas production comes from landfills and sewage sludge treatment but this is expected to change since deposition of organic material in landfills has to be reduced and is even banned in European countries. Instead biological treatment or incineration of organic material is steadily increasing. A study (From biogas to energy: a European overview, 2001) performed by Solagro, predicts a production of 210 TWh by the year 2020. This can be compared to the total world gasoline production that in 2004 was 11’000 TWh.

The majority of the countries that participated at the conference of Kyoto and followers have ratified the individual goals for the reduction of CO2 set for each country. Transport is the sector where the highest increase occurs. The European Commission predicts a 50% increase in the emissions of greenhouse gases in the transport sector from 1990 to 2010. In year 2000 the greenhouse gas emissions had increased by almost 25% from the 1990 level. It is expected that 90% of the increase is attributable to the transport sector.

Alternative fuels might help considerably to reduce emissions. This has been recognised by a number of governments which brought forward programs and legislations. A new biofuel directive (2003/30/EC) from the European Commission was approved in 2003. This directive sets targets for the European Union to gradually replace fossil fuels by biofuels. The present targets are 2% biofuels by the year 2005 and 5,75% biofuels by the year 2010. In particular, biogas as a fuel could bring substantial reductions in greenhouse gases, particles and nitrogen oxide emissions, when replacing fossil fuels, like diesel or petrol.

In 2003, the European Parliament adopted the Directive 2003/55/EC, giving common rules for the natural gas market but also for biogas and other gases from biomass in so far such gases can technically and safely be injected into, and transported through the natural gas system.