Sunday, 13 June 2010

Biogas- for a sustainable society!

Joachim Ezeji

The saying that travelling is part of education cannot be less true in all ramifications. I say so because my recent visit and tours of Sweden as a part of the Swedish International Development Agency (SIDA) sponsored Ecological Sanitation Resource class 2008.
I was among fifteen other top sustainable development professionals invited to Stockholm to undergo three weeks Ecological Sanitation Resource training. As part of the training we had schedules of visits very interesting places in Stockholm such as the Natur Centrum, the Skansen Centre, as well as the Skarpnack and Listudden neighborhoods. What I saw in these sites made me ‘dumb’. They were great places to visit by anyone who is really interested in the preservation of nature/ecology.
However my most recent visit to Linkoping, from where I scribble this piece stands out on its merit hence the desire to share my experiences with you. Linkoping is a growing city with a modest population of about 130,000 residents. It has a university that is named after it and which has a population of about 30,000 students. Basic amenities or utilities like drinking water, waste water treatment, electricity and solid waste management etc are under the management of a company called Tekniska Verken. In Linkoping there is great order and everybody seems happy.
Svenk Biogas is a 100% owned subsidiary of Tekniska Verken based in Linkoping, Sweden. Its mission is to promote the development of biogas. It works in this direction regionally by promoting and marketing the production of vehicle fuel gas and bio-fertilizer as well as the process development and biogas production concepts based on both farm produce and organic waste as raw materials.
Biogas is part of the cycle of nature. The gas is formed when organic matters decompose in an anaerobic (oxygen-free) environment. This can take place spontaneously- marsh gas is one example-or under controlled conditions, such as in a digester. In Linkoping, biogas is primarily used as fuel for vehicles, but it can be used to produce heat and electricity as well- and all this without drawing fossil fuel resources from the Earth. The biogas process also gives biological fertilizer, replacing artificial fertilizers.
Two major environmental problem areas-over fertilizing and the greenhouse effect are reduced by using biogas and bio-fertilizers. This results in a complete cycle for nutritive substances as well as for carbon dioxide.
By using bio-fertilizer the nutritive substances are returned to the farms, and by using biogas for vehicle fuel, no new carbon dioxide will be emitted to the atmosphere. You could say that the vehicles are run on solar energy which has first been stored in the green foliage and then been converted to biogas. Since biogas is a renewable form of energy it is an important part of creating sustainable environment-friendly society.
At the biogas plant in Linkoping, various waste products are converted to biogas and bio-fertilizer. Production is based on organic waste material, primarily from slaughter-house remains and the food industry, together with manure from neighboring farms.
The material is mixed into homogenous slurry in a reception tank, after which it is hygienized by steam-heating to above 70oC for at least one hour, in order to kill bacteria. After cooling, the material is pumped into a digester to be broken down by different types of microorganisms in an anaerobic environment at about 38oC. The average detention dwell time in the digester is one month, and this is where the gas is produced.
When ready, the gas is piped to the upgrading facility where it is purified in a pressurized water scrubber before it is supplied as vehicle fuel.
Next to the biogas plant the sewage water treatment plant is located. The gas produced here in the sludge digestion process can also be upgraded and used as vehicle fuel. The two plants are connected with a gas pipeline.
The biogas plant is equipped with a liquid natural gas (LNG) tank. At peak biogas demand, the LNG can be vaporized and mixed with the biogas in the pipeline, guaranteeing an uninterrupted gas supply. The material remaining after digestion, the bio-fertilizer, is cooled to 20oC and stored at the plant a day or two before distribution to farms.
All processes in connection with the production of biogas and the treatment of waste are very energy-efficient, and only a small portion of the energy content of the biogas is used in the production and distribution process.
Before biogas can be used as fuel for vehicles, it must be upgraded. Removing most of the carbon dioxide will raise the methane content to 96-98%; energy content per cubic meter roughly corresponds to 1 liter of petrol or diesel fuel. After filtering and drying, the gas meets the Swedish Standard for biogas for vehicles (SS 15 54 38).
The purified biogas is distributed to the bus depot and the public refueling station through underground pipe lines. When demand increases, it may be feasible to distribute the biogas by gas trailers to other refueling stations.
Fuelling a vehicle with biogas is done at a pressure of about 200 bars. All city buses in Linkoping run on biogas. They are refueled (slow-filling) during night stops at the depot, which has more than 60 parking spaces, making it the largest in Sweden for biogas buses
Cars are refueled at fast fill dispensers, and are usually equipped with dual fuel systems-biogas and petrol. Range varies with type of car and way of driving. The vehicles can also be refueled and run on natural gas (CNG). Biogas is the most environmentally-friendly fuel currently in existence. The combustion of biogas gives low emissions of nitrogen- and sulphur oxides, particles and uncombusted hydrocarbons.
For biological fertilizers, the quality of incoming material is essential and has to be quality assured to produce a high quality bio-fertilizer replacing artificial fertilizer on farms. Nitrogen in its organic state needs to be decomposed in the soil before it is accessible to the vegetation. During the decomposition process the organically combined nitrogen is converted into ammonium nitrogen which can be directly assimilated by the plants. This means that nutriments which the earth once gave the plants growing there, are returned, thereby completing the cycle.
As the Governor Ikedi Ohakim government trudges on with its Clean and Green Project, I am of the opinion that the project could be made greener through the adoption of the Linkoping model in Owerri city. This could be implemented if Owerri is divided into grids and the model replicated in clusters.


  1. Ah interesting idea to implement in Owerri. I did not know that you were recently in Sweden. Excellent!


Please you may respond or reply to articles posted here using this form. Alternatively, you can reach the author on: