How to reduce greenhouse gasses - Burn them

Heating a tropical swim paradise with cow manure

Many people think that greenhouse gas emissions refer only to CO₂ that is created by burning fossil fuels. But there are other greenhouse gasses as well. Methane, for example, is a more harmful greenhouse gas, trapping twenty times more heat than CO₂. Methane is estimated to be responsible for 9% of the global warming phenomenon. One of the major sources of methane is livestock manure.

A textbook example in Luxemburg

In Redange, Luxemburg, 29 cattle farmers joined together to convert the methane from their cow manure into bio-fuel for cogeneration motors. Their installation solves part of their manure surplus and has an electrical production of 1366 Mwh/year and a heat production of 2037 MWh/year. The heat is used for a sports complex and a tropical swimming pool, and in the future it will also be used for a school.

Bio-methanisation

Redange is not alone - there are about 2000 such installations up and running in Germany and Luxemburg. They have similar basic principles. The manure is transported from the stable to a digester. In summer, when manure production is low because the cows are on the field, maize and wheat can be added to the digester. A process of bio-methanisation releases methane gas, which is captured in a plastic balloon on top of the digester. In Redange, six of these digesters produce 565,000 Nm3 biogas per year.

A high-quality fertilizer

The biogas is transported via underground tubes to the cogeneration motors which can function solely on bio-fuel or, in the case of dual-fuel motors, they can also burn diesel oil. The electricity is supplied to the grid; and the heat should be used as close to the installation as possible to limit loss of energy. The product left over in the digester is a high-quality organic fertilizer, completely odourless and free of methane emissions.

Barriers to widespread application

Since the installation transforms the carbon that is bound in methane molecules into the much less harmful CO2, its environmental impact is clearly positive. However, the high cost of the installation is a major barrier to the widespread use of this technology. The investment pay-back period for this kind of installation is reasonable only in regions that grant cogeneration and green certificates. A second barrier is that cattle farms are usually located in remote areas, making it difficult to find a destination close to the farm for the cogeneration heat. Another barrier is that the digester's left-over fertilizer product is free of methane but not of nitrates. In regions with a high density of cattle per square meter, the amount of nitrates in fertilizers is strictly limited. In this case, this kind of installation does not solve the manure surplus.