Protecting the climate by cutting CO2 emissions: SPIE helps Bottrop sewage treatment plant to implement solar thermal drying facility

Published on 20 January 2021

Bottrop, 21 January 2021 – SPIE, the independent European leader in multi-technical services in the areas of energy and communications, is deploying its experts from the SPIE OSMO unit to assist the Emschergenossenschaft water board in implementing a solar thermal drying facility for sewage sludge. This is currently taking shape in Bottrop, on the site of one of Germany's largest and most advanced sewage treatment plant which treats waste water for a catchment area of more than 1.3 million inhabitants. In an environmentally friendly sewage sludge treatment process, solar and waste heat energy will dry the drained sludge. The sewage treatment plant is already energy-self-sufficient.

Burning sewage sludge without coal

SPIE OSMO will be delivering and installing on the site of the Bottrop sewage treatment plant four additional combined heat and power plants, producing a total heat output of eleven megawatts. Teams will also set up an extensive pipeline system along with equipment for the new heat station, including the associated electrical measuring and control technology. The facilities will be used for the energy supply at the sewage treatment plant and for the new solar thermal sewage sludge drying process. This marks a major milestone in terms of climate protection at the sewage treatment plant. In four digestion tanks, fermentation gases are initially produced from the sewage sludge at the Bottrop sewage treatment plant and then converted into electricity and heat by the four combined heat and power plants previously installed by OSMO. Consequently, fossil fuels are conserved, and it is possible to run the sewage treatment plant in an energy-saving way.

The second step involved burning the sewage sludge after draining. However, the necessary calorific value has previously been achieved only when coal has been added to the sewage sludge. In future, however, the solar thermal drying process is expected to extract so much moisture that a suitable calorific value will be achieved even without coal. This will involve making clever use of the thermal energy – that is, the excess heat – from the existing and new combined heat and power plants as well as that resulting from burning the sewage sludge.

Carbon-neutral sludge drying with solar energy

The process takes advantage of the Sun as a natural source of energy. There are 32 drying facilities, not dissimilar to greenhouses, standing on a 60,000-square-metre site – a gigantic area of Bottrop where sewage sludge is dried in a carbon-neutral way with the addition of solar energy. SPIE will be implementing the distribution of thermal energy inside the drying facilities and installing an extensive network of pipes in the buildings, on a new pipe bridge that is to be erected and in the new heat station. “We are delighted to have the chance once again to help the Emschergenossenschaft with their commitment to greater climate protection on this project because we have focused on sustainable energy generation and usage. Combined heat and power is a central element of our portfolio, but innovative systems such as the solar thermal drying of sewage sludge involved in this case are also a perfect fit for our services,” says Hartmut Vahrenhorst, Managing Director of SPIE OSMO. Dr Emanuel Grün, Chief Technology Officer of the Emschergenossenschaft, mentions some specific figures. “With the solar thermal drying facility, we will save around 20,000 tonnes of coal per year, which will cut our annual CO2 emissions by roughly 60,000 tonnes. This will make us more environmentally friendly and put us right at the cutting edge of development.

Conserving resources, promoting climate protection

We are thrilled to be involved in this project because climate protection is one of the key areas that we focus on as a multi-technical service provider. With our work on implementing the state-of-the-art drying facility at the Bottrop sewage treatment plant, we are making our own contribution by helping to conserve resources and boost energy efficiency. We are certain that economic progress relies on protecting and making sustainable use of the environment and ecosystems. Creating a carbon-neutral future currently offers one of the biggest market opportunities,” says Rüdiger Graf, Head of Business Development & Sales at SPIE Deutschland & Zentraleuropa.

Even once the project is complete, SPIE will remain a dependable partner to the Emschergenossenschaft. With its specialists from SPIE OSMO, the multi-technical service provider will continue to be responsible for keeping the combined heat and power plants, and all their peripheral equipment, running smoothly for the next four years as part of a maintenance contract.