Challenging Odours within Biogas

In a modern world, Biogas has the potential to replace a large part of fossil fuel consumption. The possibility to generate energy from a wide variety of sources, environmental impact and profitability create an attractive ground for more and more companies to invest in the renewables industry. A good example of such a biogas plant is in Alvesta, Sweden. This plant specializes in turning slaughterhouse waste into an effective source of energy which powers up local houses and businesses in the surrounding area. While being one of the most strategically active plants in the municipality, Alvesta Biogas started appearing in the news, however not in the light they wanted to.

The process of generating slaughterhouse energy starts with the storage of the biomass in hygienization tanks. During this process the biomass is heated up in order to remove the liquid elements from the material as a pre-processing stage. As a result of that heat, a strong and irritating smell started to escape the tanks and the facility and spreading around the neighbourhood communities. This has caused a mass outrage with continuous complaints and threats from the municipality. The Biogas plant is now threatened to be shut down which could leave the area without energy supply and the workers unemployed.

When Scandinavian Centriair AB had received the request to help Alvesta Biogas solve their odour problem, nobody knew what was going to come. With extensive experience in the field of waste and biogas, Centriair experts assumed that the presence of H2S, Ammonia and other Volatile Organic Compounds (VOCs) would be the main elements causing the unpleasant smell. Since the customer has not done its odour measurements, Centriair team together with ÅF consultants had gathered samples which were later analysed in the lab. The results were shocking as the VOC concentration has showed 8 000 000 OU and 8 000 ppm H2S in the gas stream. To get an idea of how unpleasant that smell can get, we can say that at 0,000047 ppm of H2S a human nose can already detect the odour. According to the statement of ÅF consultants, this had been the highest VOC concentration that they have witnessed in Sweden.

The task was not easy since there are very few technologies in the market that can handle such extreme concentrations. For Centriair there was only one solution: DEO™ – catalytic conversion technology. DEO-100™ is a regenerative catalyst system for elimination of VOC and odour emissions from industrial processes. VOC and odour compounds are eliminated through patented mesh catalyst technology allowing for optimized and compact reactor geometry, large catalyst area and heat capacity. After the installation the smell seemed to disappear, and it became more bearable to stand around the plant. Knowing all the challenges of this application, Centriair team has done another round of sampling at the outlet of the DEO-100™ system. The test results indicated 99,6% reduction rate on VOCs and H2S compounds with less than 1 OU/M3 in the distance of 200 meters from the plant. This was a win-win situation for everyone.

In conclusion it is important to point out the necessity of odour treatment within Biogas plants. Alvesta Biogas is a good example of how ignorance of the problem could lead to sever consequences. It does not matter what a plant decides to use as a feedstock: it could be manure from animals, green waste from farms, sewage from the waste water treatment plants, it will all generate unpleasant smell for the staff and for the unlucky people living around biogas sites.