A new report from the University of Copenhagen shows that burning wood is much more climate-friendly than coal and slightly more climate-friendly than
FACULTY OF SCIENCE – UNIVERSITY OF COPENHAGEN
ENERGY A new report from the University of Copenhagen shows that, in the long run, burning wood is much more climate-friendly than coal and somewhat more climate-friendly than natural gas. For the first time, the researchers quantified what the conversion of 10 Danish CHP plants from coal or natural gas to biomass means for their greenhouse gas emissions.
Heat the system
Energy generation is responsible for a large part of Denmark's greenhouse gas emissions. In 2018, more than 20 percent of greenhouse gas emissions were released through the generation of heat and electricity (9.4 of 48 million tons of CO2). Photo: Getty
Converting Danish district heating power plants into wood biomass (wood chips and pellets) has benefited the climate and is the more climate-friendly option compared to coal and natural gas. This emerges from a new report from the Institute of Earth Sciences and Natural Resource Management at the University of Copenhagen.
The study is the first retrospective study by researchers on what a conversion to wood biomass means for greenhouse gas emissions in ten Danish CHP plants – and thus the climate impact of replacing coal or natural gas in favor of wood biomass.
Among other things, the researchers calculated the so-called carbon payback period for each plant, i.e. H. How long it takes for the conversion into wood biomass to have a positive effect on the climate.
“Our results show that the transition from coal to wood biomass has had a positive effect on CO2 emissions after an average of six years. The transition from natural gas took between 9 and 22 years in most cases and 37 years in one case before CO2 emissions were reduced, ”says Associate Professor Niclas Scott Bentsen of the Department of Earth Sciences and Natural Resource Management, one of the authors of the Report is.
Reduction of CO2 emissions
The researchers also examined the total CO2 emissions from the three energy sources over a period of 30 years, which is the life expectancy of a CHP power plant.
Moving from coal to biomass resulted in a 15 to 71 percent reduction in CO2 emissions, while moving away from natural gas resulted in a -4 to 19 percent reduction in emissions.
The fact that in one case the emissions after 30 years as a result of the conversion were -4 percent is partly due to the fact that burning natural gas releases less CO2 in terms of energy content than burning wood. The respective plant had notable changes in its product portfolio.
"If there are such large fluctuations in the numbers, it is because the payback period and the amount of CO2 emissions saved are significantly affected by the type of fuel it is made from and other alternative uses for the wood," says Associate Professor Niclas Scott Bentsen
Forest residues are best for the climate
The 10 Danish CHP plants collected 32 percent of their wood biomass from Danish forests, while 41 percent came from the Baltic states, seven percent from Russia and Belarus and seven percent from the USA. The type of wood biomass used and the distance that had to be transported were also factored into the carbon budget, according to Professor Bentsen.
“For the typical plant, which was once coal-fired but now uses wood from all over Denmark and only uses forest residues that cannot be used for other products, the payback period was about a year. The 30-year savings were up to 60%, ”explains Niclas Scott Bentsen.
Wood has tremendous potential to displace high carbon building materials like steel and concrete, so it is an important aspect of the green transition.
"Our study shows that the extent to which wood is used for construction or other forms of production where the long life of wood can bind CO2 is even better for the climate than using it as fuel," says Niclas Scott Bentsen.
The method used in the study involves an analysis of time series of individual plants that includes the time before and after the conversion of fossil energy sources to wood biomass. The analysis included, among other things, specific knowledge of the type of fuel used, where the fuel came from and what alternative uses the wood might have.
Energy generation is responsible for a large part of Denmark's greenhouse gas emissions. In 2018, more than 20 percent of greenhouse gas emissions were released through the generation of heat and electricity (9.4 of 48 million tons of CO2).
16 percent of Denmark's total energy consumption comes from the burning of wood biomass. For comparison: 7 percent of energy consumption comes from wind turbines.
In order to reduce carbon recovery time and atmospheric CO2 emissions, suppliers should focus on using residual biomass (branches and crowns from logging or residues from the timber industry that have no other use), biomass from productive forests and reducing long-term Concentrate transport routes.
The project is funded by Danish Energy and the Danish District Heating Association. The project was followed by a follow-up group made up of representatives from the Council for Green Conversion, the Danish Society for Nature Conservation, Concito and the Danish Energy Agency. The report is reviewed by internationally renowned researchers.