Better biomass burning helps reach renewable energy targets
Amid an urgent need to cut carbon emissions to combat climate change, EU-funded researchers have developed a new generation of highly efficient power plants for generating heat and electricity from biomass.
© Gerhard Seybert #134574292, source:stock.adobe.com 2020
Heating and cooling are responsible for almost half of the EUs total energy use. In the battle to reduce carbon emissions, it is vital that renewable sources of energy become more efficient and more widely used.
Representing over 90 % of all renewable heat generated in 2014, biomass could play a critical role. Improving the technology used in biomass-fuelled combined heat and power (CHP) plants, which generate electricity and capture the usable heat that is produced, has significant potential for helping to meet sustainable energy targets.
The EU-funded BIOFFICIENCY project set out to identify and tackle issues that currently restrict the productivity of CHP plants.
The intensive, three-year project concluded in October 2019, having succeeded in increasing CHP plant efficiency and, as a result, reducing emissions (carbon dioxide, particulate matter, carbon monoxide, nitrogen oxides and sulphur dioxide). The research team has also created a blueprint for future biomass-fuelled CHP plants.
We aimed to develop a holistic foundation for the next generation of large-scale biomass CHP plants, utilising their huge potential for cost-competitive energy and heat generation in environmentally friendly conditions, says project coordinator Sebastian Fendt of the Technical University of Munich in Germany.
Not only could the switch towards renewable energy solutions like biomass create over half a million new jobs across the EU, but it would also lower the amount of emissions by replacing coal-based energy generation.
When it comes to burning biomass, ash-related issues are one of the main bottlenecks. For example, some types of biomass produce ash that corrodes the power plants inner surfaces at high temperatures. This potentially leads to damage and therefore increases maintenance costs. It also limits the temperature of steam, which in turn reduces the overall efficiency of the combustion process.
One of BIOFFICIENCYs major investigations tested a variety of heat-exchanger materials inside modern power plants to find those most resistant to corrosion. Researchers identified ways of improving CHP plants through the choice of different heat-exchanger materials and by using new cleaning routines.
The team used test facilities across Europe to develop a model of how fly ash is formed during biomass combustion.
By evaluating existing fuel pretreatment methods, the project found that it was possible to significantly reduce emissions and deliver improvements in the fuels physical and chemical properties. Optimising additives and introducing novel pretreatment methods such as steam explosion, hydrothermal carbonisation, and torrefaction has reduced the production of harmful emissions and allowed CHP plants to use a broader range of biomass feedstock.
Furthermore, a large-scale experiment tested out advanced sensor systems designed to automatically blend fuels and incorporate additives.
Ultimately, the projects combined findings have already been used by many partners. For example, Mitsubishi Hitachi Power Systems designed a new 300 thermal megawatt (MWth) biomass-fuelled CHP plant that reaches the standards and targets demanded by the EUs Renewable Energy Directive II.
Project partner Valmet recently sold their pre-hydrolysis reactor the world's first continuous steam explosion pretreatment plant for challenging biomasses. Other findings by BIOFFICIENCY were used to improve Valmet's Superheater KCl Corrosion management system for controlling corrosion caused by alkali chlorides.
The researchers also developed ideas for using the by-products to make the process even more sustainable. We tested different ways of using ash that results from the combustion process instead of treating it as a waste product, explains Fendt. Using it in construction materials, like geopolymers or calcium-silicate blocks, has proved to be one very promising application.
ENGIE, another project partner, has found ways of using ash to create construction materials such as geopolymers and calcium-silicate blocks. The company is currently looking into how it can bring these promising applications to market.