Municipal authorities in Sweden have been converting waste materials into usable biogas for several years. In 2005, in an attempt to make public transport more environmentally friendly, the world’s first train to be run solely on biogas was developed by a private company, Svensk Biogas.
The Swedish Environment
Sweden has strong environmental policies. The Swedish Parliament has established 16 environmental quality objectives, including “Clean air” and “Good-quality groundwater”, to guide Sweden towards a sustainable society. These objectives function as benchmarks for environment-related development in Sweden. The overriding aim is to solve all the major environmental problems within one generation. There are two targets that are encouraging developments in the biogas area:
- Reducing climate impact.
- A non-toxic environment.
With stricter regulations for landfilling being introduced there is a move towards alternative treatment methods for waste. For example, many municipal authorities in Sweden create biogas from sewage treatment plants, waste water and municipal food waste. This biogas has generally been used to power household water heating systems and in a purified and compressed form as fuel for municipal transport vehicles.
Biogas is one of the least environmentally harmful fuels that is economically available today. It is based on biologically produced substances and is produced through a recirculation process. It does not contribute to the carbon dioxide (CO2) content in the atmosphere. Methane, the main constituent of biogas, is also a ‘greenhouse’ gas, but as a fuel it can be harnessed and put to good use. Emissions of hydrocarbons, carbon monoxide (CO) and nitric oxides from its production and use are small. In addition to the environmental aspect, biogas has the advantage that it can be produced locally and supply is not dependent on imports.
Incentives are offered to those who opt to use biogas cars:
- Parking is free in many areas.
- For companies buying a biogas car for their employees the tax on the company car is lowered.
- Biogas is free of tax, so it costs 20-25 per cent less than petrol.
Hence the private market for biogas-fuelled cars is increasing, even though the cars themselves are more expensive as they are usually equipped with dual fuel systems – biogas and petrol. Sweden has around 800 biogas buses, more than 4500 cars that run on a mixture of petrol and either biogas or natural gas, and 55 biogas filling stations.
European directives are urging governments to promote biofuels and other renewable energy sources for transportation as replacements for petrol and diesel, Sweden is aiming for a target of 3 per cent in 2005, which is the highest target in Europe, where most countries have set a target of around 2 per cent.
Potential for Public Transport
Linköping, Sweden’s fifth largest city, has 67 buses, 10 trolley trucks that pick up waste, and 90 taxis that run on biogas. Carl Lilliehöök, the head of Svensk Biogas, wanted to see if this power source could also be used for trains.
About 97 per cent of Swedish train traffic runs on electricity, through power lines that run over the tracks. The other 3 per cent runs on diesel. Carl Lilliehöök believed that diesel trains could be converted to run on biogas. Two Volvo biogas engines, similar to those used in biogas buses, were fitted to the base of a diesel train. The biogas train, Amanda, is equipped with eleven canisters containing enough gas to run for 600 kilometres (375 miles) before needing a refill, and can reach a maximum speed of 130 kilometres (81 miles) per hour.
The train can carry up to 54 passengers on an 80-kilometre (50-mile) stretch between Linköping in south-central Sweden and Vastervik on the country’s east coast.
The new train, development of which cost Svensk Biogas 10 million kronor (€1.07 million, US$1.3 million), went into service in September 2005. The train is operated by SJ, the Swedish railway. The biogas train emits just a small fraction of the carbon dioxide released by diesel engines. Although the cost of running the train is 20 per cent higher than with conventional diesel, with rising fuel prices this could soon be cost competitive.
It has been estimated that humans directly consume only 68 per cent of a chicken, 62 per cent of a pig, 54 per cent of a cow and 52 per cent of a sheep or goat. Every year, therefore, more than 10 million tonnes of meat, derived from healthy animals yet not destined for direct human consumption, are produced in the European Union (EU).
- It takes 2.5 cows to produce enough biogas to move the train 1 mile.
- One cubic metre of clean biogas is approximately the equivalent of 1 litre of petrol.
- Biogas does less damage to the environment because it reduces the amount of waste going to landfill and has cleaner emissions.
Regulations on how to deal with these animal by-products have been adopted by the European Parliament. These not only cover food safety, but also introduce stringent conditions throughout the food and feed chains requiring safe collection, transport, storage, handling, processing, uses and disposal of animal by-products.
Animal by-products are the parts of a slaughtered animal that are not directly consumed by humans, including dead on farm animals and catering waste (i.e. waste food originating from restaurants, catering facilities and kitchens) that contains or has been in contact with meat products, whether cooked or uncooked. Some of these products find other uses, for example in bone-meal, pet foods, fats, gelatine, collagen, and other technical products such as glue, leathers, soaps and fertilisers. The alternative is their destruction, most often by incineration. If used for biogas the total energy potential from waste generated during slaughter is about 1300 megajoules (MJ)/cattle and about 140 MJ/pig.
EU Animal By-Products Regulation
The EU Animal By-Products Regulation came into force across the European Community on 1st May 2003. This divides animal by-products into three categories:
- Category 1 is high risk and must be incinerated.
- Category 2 is material unfit for human consumption. Most types of this material must be incinerated or rendered (melted down).
- Category 3 is material that is fit for but not destined for human consumption. It is this category in which may be incinerated, rendered or transformed in a composting or biogas plant.
Biogas plants generally treat a combination of materials and are therefore subject to the strict standards, namely:
- The process must be in-vessel – controlled anaerobic digestion is by definition in-vessel.
- The maximum particle size of material is 12 mm.
- All material must be pasteurised at a minimum temperature of 70°C for one hour.
- Procedures must be adopted to prevent recontamination of the final product with raw waste.
- Samples of the final product must be free of salmonella.
Svensk Biogas uses 55,000 tonnes of waste materials a year from slaughter houses, manure from local farms, waste water from sewage plants, waste food and milk products. The mixture is biologically treated by anaerobic digestion to produce 4 million cubic metres of clean biogas, mostly methane.
The main stages in the biogas production process are:
- The material is mixed into a homogenous slurry in a reception tank.
- It is steam-heated 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 bacterial micro-organisms in an anaerobic (without oxygen) environment at about 38 oC. It normally takes about one month for the gas to be produced.
- Once the gas is ready, it is pumped to the upgrading facility where it is purified in a pressurised water scrubber and the methane content is boosted to around 97 per cent by removing the carbon dioxide. After filtering and drying the biogas meets the Swedish Standard for biogas (SS 15 54 38). It can then be used as vehicle fuel.
The sanitised material remaining after the digestion process can be used as a fertiliser and soil improver. It is more valuable than ordinary manure because it has better nitrogen availability and less odour. It is sold back to local farmers, and the same trucks that bring the farm manure to the plant is used to transport the fertiliser back to the farms.
Evaluations on the biogas plant at Linköping show the plant is working well.
Future plans include a new biogas plant at Norrköping that will produce biogas from organic materials such as agricultural crops and waste. Initially it will produce 1.5 million cubic metres (m3), but this should increase to 2 million m3, and if all goes well it is hoped to expand the plant to a capacity of 4 million m3 in the near future.
Hands On would like to thank Carl Lilliehöök, the head of Svensk Biogas, for his help in putting together this case study.
Svensk Biogas www.svenskbiogas.se
ITDG Technical Briefs answers.practicalaction.org
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