Adding Wood to Fossil Fuels Could Reduce Carbon Emissions

The use of fossil fuels poses an increasing risk to the environment. According to the initial outcomes of a year-long study performed by thermal engineers of Tallinn University of Technology, this could be made more eco-friendly by the addition of wood.

While looking for less polluting methods of energy production, it was found that using increased amounts of biomass as a source of raw materials provides a better way to utilize fossil fuels and curb emissions.

According to Professor Alar Konist, Head of TalTech’s Laboratory of Fuel and Air Emission Analysis, who leads the study, “We used thermogravimetric analysis in our research. In modern laboratory conditions, the use of a high-speed furnace for thermogravimetric analysis allows determining reactivity of wood at different temperatures and mass percentages.”

Professor Konist added, “Our goal was to study the kinetics of combustion of biomass - in this case wood and oil shale, with the aim to maximise the amount of biomass.”

In thermal engineering, one of the possibilities to minimize carbon dioxide (CO₂) emissions is to decrease the share of oil shale fuel and use renewable raw materials as alternatives.

In this research, scientists from the Tallinn University of Technology used one of the ubiquitous renewable natural resources—wood—for performing analysis of the co-combustion of oil shale and wood. Analysis of mixtures including up to 40 mass percent of wood was performed.

Today we can say that use of the mixture of fossil fuel and biomass in the Estonian CFB boilers is the least damaging to the environment. For example, the efficiency of our most well-known modern green electricity producer, the Auvere Power Plant is 40%, while in other cogeneration plants that produce electricity in addition to heat the efficiency still remains below 30%.

Alar Konist, Professor, Head of Laboratory of Fuel and Air Emission Analysis, TalTech

In contrast to burning solid bio-fuels, the burning of fossil fuels leads to the emission of CO₂ into the biosphere circulation. This is because solid biofuels are part of the biogeochemical cycle. There are two major environmental concerns associated with fossil fuels. Firstly, flue gases include several contaminants emitted into the atmosphere apart from CO₂, and secondly, ash is formed during combustion.

The results of our research show that the emission concentration of pollutants in the flue gas can be controlled at the lowest optimal combustion temperatures of 700-800 °C. The formation of the other harmful factor—ash—can be reduced by almost 50% by adding wood to the oil shale. Such ash has added value: due to added wood, the quality of the ash is suitable e.g. for use (or more accurate to say “for re-use”) as a raw material for production of green cement.

Professor Alar Konist, Head of Laboratory of Fuel and Air Emission Analysis, TalTech

The future areas of focus are carbon capture and utilization (CCUS technologies), gasification, and oil shale pyrolysis. This will be addressed by power and heat engineers in the short term. With climate targets becoming more stringent, Europe is facing situations where the consumption volumes have increased, whereas the production volumes have declined significantly.

This implies that Europe has to import energy, irrespective of its stringent environmental regulations. Consequently, this has led to the conclusion that cheaper energy generated in accordance with low environmental needs could be sold at a lower price. Thus, sadly, the energy generated by cleaner technologies is not competitive in Europe under existing market conditions.

I am convinced that as long as our energy production continues to be market-based, we cannot unfortunately rely on major solutions that value the environment, such as implementation of carbon capture technologies, etc.

Professor Alar Konist, Head of Laboratory of Fuel and Air Emission Analysis, TalTech