Waste to Energy Cuts 200,000 tCO2 Annually in Gothenburg
Gothenburg’s system of incinerating waste to make electricity and heat is highly efficient. Benchmarked against other European countries, the system compares very favorably, generating 3.3 MWh per ton of waste for heating (27% of the city) and electricity, reducing landfill to a small fraction of the total waste collected, and cutting emissions by over 200,000 tCO2 annually. By generating energy from waste, 25% of the City’s CO2 emissions from energy consumption have been cut.
What is it?
An integrated waste system that collects, sorts and burns Gothenburg’s 345,000 tons of rubbish annually. The incinerated waste creates energy, which is used for heating and electricity. Waste is only removed by contractors if it has been separated for recycling, meaning 19% of total waste and 33% of household waste is recycled.
How does it work?
In Gothenburg, waste management services are contracted out to various private companies, such as Renova, IL Recycling and RECI AB. The local authority is responsible for the collection and treatment of household waste, which generates around 150,000 tons per year. A similar volume is generated by industry and business. Waste management companies bid for tenders in order to collect, treat and dispose of this waste.
Some 45,000 tons in packaging waste is collected at over 350 points around the city. Here the “producer pays” principle applies – citizens have a duty to sort and deposit various types of waste, such as glass, metal cans, cardboard, newspapers and batteries, with industry associations (charging fees to their members) organizing the contracting of waste management firms to handle the waste. Companies can opt out of this system but are then legally obliged to set up alternative measures.
Renova is responsible for around 80% of waste management activity in the city of Gothenburg and is owned by 11 municipalities in the Västra Götaland region, and for this reason, this case study will concentrate chiefly on this company’s activities.
Renova competes against private companies on the open market. In addition to its work in Gothenburg city, it collects waste in 4 neighbouring municipalities. In 2006, the company handled a total of 890,000 tonnes waste. They strive to maximize recycling, reuse and recovery in the waste handling process. Collected waste is sorted at a range of facilities around the city, each specializing in particular waste types – 5 centres handle household waste, 2 industrial waste, and other facilities exist handling, for example, materials for composting.
- In 2006, material recovery of 105,000 tons was achieved and 18,000 tons of soil and fertilizer was produced.
- Much of the remaining waste was sent for incineration at the waste-to-energy plant in Sävenäs, which opened in 1972. Renova has a 15-year service contract for incineration in 11 municipalities and this facility creates energy and electricity for the district heating system in Gothenburg.
The Sävenäs plant has three boilers with a shared capacity of 150 MW that are able to process 59 tonnes of waste per hour. Flue gas condensation systems and AHP-cooling of process water generates an additional 40 MW, meaning the total power output of the plant is 190 MW.
Together with waste heat recovered from industrial processes, the heat and electricity generated from incinerated waste forms the base load for the city’s district heating system. Renova provides 27% of the 3970 GWh required for district heating – waste heat recovery from industrial sources provide 30% (principally from the Shell and PREEM oil refineries); ground source heat pumps 10%; biofuels 16%; natural gas 16%; and oil, just 1%. Fossil fuels are only used in winter, when the Swedish climate is at its most extreme. In summer months, incineration and waste heat recovery covers the city’s district heating needs.
In 1974, around 200,000 MWh of energy was produced through the incineration of almost 200,000 tonnes of waste. By 2006, the volume of waste had risen to over 400,000 tonnes, yet the total energy produced had soared six-fold, to over 1,200,000 MWh. This is due to the introduction of new boilers, flue gas condensers, other technologies and increased efficiency in sorting and separation of waste. Technological advances also helped reduce the amount of dust and particulate matter from 201,000 tonnes per year in 1981 to 4,400 tonnes per year in 2005.
In 2006, 438,010 tonnes was sent for incineration, after which 86,795 tonnes of slag and 16,481 tonnes of fly ash and sludge remained. These were recovered and used as part of the sealing process at landfill sites. In total, 1,418 GWh of energy was produced from incineration – 1,212 GWh for heating and 206 GWh for electricity.
Renova’s activities in sorting, recovering, recycling, composting and incinerating mean that of all the waste that is collected, only 8% remains for landfill. From 2008, new rules apply to landfills constructed in the EU – many sites will close, meaning companies like Renova are seeking ways to reduce both the overall volume of waste and the fraction that currently goes to landfill.
Benchmarked against other European countries, the system in Gothenburg compares very favourably - around 3.3 MWh per ton are generated for heating and electricity. Renova outperforms many other companies in Sweden, where similar levels of heating are generated but generally levels of electricity production are much smaller.
In Denmark, the share of heating is typically much smaller. Switzerland produces similar volumes of electricity but far less heat. In other countries, the focus is almost always on electricity or heat, rarely both – this is partly due to the Scandinavian need for secure heating supplies in winter.
Gothenburg has achieved a reduction in the emission of harmful elements and chemicals in the incineration process. For example, from 1989 to 2006, the volume of waste incinerated almost doubled, yet the levels of mercury emitted in the burning process fell from 64kg per year to 2kg. As mentioned before, levels of dust and particulate matter also fell dramatically.
CO2 emissions reductions
Waste-to-energy production saves the equivalent of 130,000 tonnes of oil per year. Against a hypothetical measure of energy produced through burning of oil, waste-to-energy production saved the city an estimated 205,060 tonnes CO2 in 2006 – a figure that appears to be consistent over the past six years.
The system used by Renova is highly efficient and has displayed incremental improvements over the past twenty years. In sum, these amount to huge energy efficiency savings, in which total energy produced from incineration has gone up six-fold in a period when volumes of waste incinerated have only doubled. Moreover, large volumes of waste have been diverted from landfill and recovered.
It is difficult to estimate the total cost of establishing a waste-to-energy system similar to Renova’s, as the system has developed incrementally over a long period of time (the company was formerly an agency of the municipality). Renova suggest the total system cost, at today’s prices, amounts to a sum in the region of 3-4 billion SEK (between $450-600m USD).
- The construction of a fourth boiler at Renova’s Sävenäs facility will cost $92.5m USD (600m SEK).
- Renova’s turnover totals around $162m USD (1 billion SEK) – of this, 546 million SEK relates to waste and treatment revenues; 221m SEK to sales of energy, heat and electricity; around 280m SEK to collection and transport revenues; and 22m SEK to other revenues.
- The production of electricity at the Sävenäs waste-to-energy plant is particularly important, as it reduces the tax burden of incineration for Renova. In Sweden, there is a tax on all landfill and a further tax on incineration, with the amount varying if electricity is produced. The aim is to reduce the volume of waste incinerated or sent to landfill
- Thus, the ashes from incineration which are used to seal landfills are taxed twice, but as both the volume of landfill has decreased and electricity is generated through incineration, this is cost-effective.
An area of great potential in Gothenburg relates to organic waste. At present an incentive-based scheme exists whereby citizens can commit to organic waste separation in return for reduced waste service fees. However, uptake of the scheme is low, as 80% of residents live in flats and housing associations can decide whether to embrace the scheme or not. If a housing association joins the scheme, they must then provide extra facilities for residents. At present, only 12 tonnes of separated organic waste is collected, but the city believes this could rise to 50 tonnes in the future.
Another new scheme is the Alelyckan recycle and reuse center, which aims to encourage people to think about what they are throwing away. A drop-off facility is strategically located before a household waste deposit point and offers people the opportunity to leave goods that they no longer want but somebody else can use.
Staff at Alelyckan then collect these materials and sell them in various shops that offer jobs to the long-term unemployed. The idea is to benefit the community, prevent incineration and landfill of potentially useful items, and more generally to make citizens think about what they consider waste and establish a waste reduction culture. This facility cost around €400,000 to construct and €850,000 per year over 20 years to operate.
The greening of collection trucks is another developing area. Since 1994, Renova has used 50 Volvo CNG trucks as part of its waste collection fleet. More recently, the company was part of an EU project piloting CNG-electric-hybrid trucks. These vehicles use hybrid technologies during the stationary phases of work, ie. loading and compacting. Swedish studies have shown waste collection trucks stand idle for 60% of their service time, meaning there is scope for significant GHG reduction.
Electric sensors mean the trucks only use the correct amount of energy for lifting and advanced catalytic converters reduce GHGs. Route planning software helps drivers optimize their collection routes and staff undertake “Heavy Eco-driving” courses to learn how to drive more efficiently. Compared to conventional diesel engines, the electric-hybrid technology emits between 70-94% less NOx, HC, CO and PM, but only small CO2 reductions. Compared to CNG vehicles, the electric-hybrid cuts 40% of CO, PM and CO2, yet increases NOx by 1% and HC by 4% due to engine restarts.
Moreover, the new catalytic converters have 80% efficiency compared to 23-26% in old models. Fuel consumption from electric-hybrid collection is reduced by 20-40% in the inner city; electricity consumption during loading/compacting is 2.1kWh per tonne or 5 MWh per year; total CNG needed by electric-hybrid per year is 90 MWh. However, total costs including staff and operations, compared to both diesel and CNG vehicles, are approximately the same, making the technology viable and worthy of expansion.