Forests key to achieving climate goals: Study

Trying to tackle climate change by replacing forests with crops for bioenergy power stations that capture carbon dioxide could instead increase the amount of CO2 in the atmosphere, scientists say.

Biomass Energy with Carbon Capture and Storage (BECCS) power stations are designed to produce energy and store the resulting carbon dioxide (CO2) in bedrock deep underground.

However, a study led by the University of Exeter in the UK suggests that converting large land areas to growing crops as biomass for BECCS would release so much CO2 that protecting and regenerating forests is a better option in many places.

"The vast majority of current IPCC scenarios for how we can limit global warming to less than two degrees Celsius include BECCS," said Anna Harper from the University of Exeter.

"But the land required to grow biomass in these scenarios would be twice the size of India," said Harper, lead author of the study published in the journal Nature Communications.

This motivated the researchers to look at the wider consequences of such a radical change in global land use.

They used a cutting-edge computer model of global vegetation and soil and presented it with scenarios of land-use change consistent with stabilising the climate at less than 1.5 degrees Celsius and two degrees Celsius of global warming.

The researchers warn that using BECCS on such a large scale could lead to a net increase of carbon in the atmosphere, especially where the crops are assumed to replace existing forests.

"In some places BECCS will be effective, but we have found that in many places protecting or regenerating forests is much more sensible," said Tom Powell, from the University of Exeter.

How well BECCS works depends on factors such as the choice of biomass, the fate of initial above-ground biomass and the fossil-fuel emissions offset in the energy system - so future improvements could make it a better option.

"Our paper illustrates that the manipulation of land can help offset carbon dioxide emissions, but only if applied for certain quite specific locations," said Chris Huntingford of the UK Centre for Ecology and Hydrology.

"To meet the climate change targets from the Paris agreement, we need to both drastically reduce emissions and employ a mix of technologies to remove carbon dioxide from the atmosphere," Harper added.