Burying biomass in the ground under anoxia. This is the idea of the American firm Kodama Systems, which has received more than six million dollars in funding from, among others, Bill Gates’ climate and technology fund. The US Forest Service, Forbes reports, has also put money into helping transport the surplus biomass from tree thinning (cutting down trees to leave the best trees in a forest with more room to develop) to wooden vaults where the biomass is buried, “sequestering carbon for centuries.” Something that is common in forest management, such as removing biomass (to avoid fires, for example), is somewhat shocking in this idea, because why bury the felled trees? Kodama says it is to prevent them from decomposing and emitting CO2, but “if you want to sequester carbon from the trees, use them in paper, in construction, in barrels. In any product that makes money and doesn’t burn, but bury them? “It is logical that this wood should replace materials and products of fossil origin, not bury them,” says Patricia Gómez, manager of the Confederation of Forestry Organizations of Spain (COSE).
«Dead wood in the forest is good for biodiversity and helps to keep water in the forest for longer, preventing runoff. Its role is basic in the natural environment, but it can also be sequestered in furniture. Even if you bury the wood, there will always be some oxygen and it will decompose, which will generate CO2 again,» says Jordi Vayreda, researcher at the Centre for Ecological Research and Forestry Applications (Creaf).
The information about the Kodama project, published by Forbes, together with the statements about the absurdity of planting trees made by Bill Gates at a climate summit held by The New York Times (“I don’t plant trees… Are we science people or idiots?”) raised many eyebrows a few months ago and have put on the table a debate about reforestation and carbon offset projects. Gates’ statements are curious when the objective of Kodama, a company that he finances, is precisely to plant new trees and sell carbon credits to companies that need to offset their emissions.What should reforestation projects be like so that they really absorb CO2? Are they a good solution to fight climate change? Is there a danger that these projects will generate uniform forests with only fast-growing species? Is it dangerous to understand a forest only by its value as a carbon sink? “It is good to have everything: young forests, mature forests, plantations. Mature forests fulfill an ecosystem function, they can be refuges for biodiversity, etc. When reforestation is planned, the purpose of the forest must be considered in order to decide which species to plant (fast-growing species such as poplars or eucalyptus can be interesting for absorbing carbon more quickly and making industrial use of it) and, above all, we must not forget that forest management must be carried out (clearing, thinning…), also in mature forests. Both actions are necessary,” says Patricia Gómez.
Since 2000
The truth is that the carbon market and reforestation projects have become a common action of the private sector since the beginning of 2000. Forests are, together with soil and oceans, the largest carbon sinks on the planet. Carbon is stored in the long term in trees through wood and in the soil thanks to vegetation. Naturally, it is estimated that they absorb 29% of anthropogenic emissions, Another 26% is removed by the ocean, and the other 45% accumulates in the atmosphere.
For Jaime Martínez Valderrama, a researcher at the University of Alicante and the CSIC Experimental Station for Arid Zones: “The first thing is to conserve. There is a rush to reforest, but we have to bear in mind that the first thing is to conserve the forests that exist, especially the primary ones. In Europe we buy many raw materials from other continents at the cost of deforesting large primary forests, in the Amazon, for example. The most important thing is to conserve these masses, because they are the ones that work best to capture carbon. The largest CO2 deposits are in the soil, and when there are changes in land use and forests are removed, that carbon goes into the atmosphere. Almost half of the carbon comes not from burning fossil fuels, but from this change in land use. So agriculture has generated almost half of the emissions. On the other hand, establishing a forest takes a long time. A forest is considered to be fixing carbon after 100 years, which is the average lifetime of carbon in the atmosphere. Large-scale reforestation has been going on since 2000, so we won’t see until 2100 whether all this is working or not.
The carbon market is voluntary. There are calculators that determine the volume of CO2 that a reforestation project will set based on the species to be planted and other parameters such as the condition of the forests, the density per hectare, etc. “We are not very convinced by this method and we see that it creates a business bubble for companies that are dedicated to projects and that decide the area of action, the species, calculate the carbon that will be absorbed and sell the credits, but then you find all kinds of companies; some serious and others that do not really monitor the specimens?” asks Patricia Gómez.
According to an investigation carried out a year ago by The Guardian, the German weekly Die Zeit and the investigative journalism organisation Source Material, more than 90% of rainforest carbon offsets made by the largest certifier are worthless, meaning they are do not represent genuine carbon reductions. «The first thing to have is an overview of carbon credit projects: most are linked to tropical forests and in theory are intended for avoidance projects, meaning that their objective is to prevent forest stands from disappearing. However, in most cases they cannot prove carbon sequestration or that deforestation is not taking place. In addition, some of the areas where these projects are carried out are already protected by other means and, in many cases, land ownership issues arise. Most credits are linked to this. However, since 2021 we have seen that the carbon market volume has been reduced by up to five times,» explains Marcel Llavero-Pasquina, coordinator of the Global Atlas of Environmental Justice (EJAtlas.org), and researcher at the Institute of Environmental Science and Technology of the Autonomous University of Barcelona (ICTA-UAB).
Credits for management
For Jordi Vayreda, a researcher at Creaf, the first thing is to conserve, then to worry about the forest management of mature forests and reforestation, “especially in cases of soil erosion, but here we are talking about recovering vegetation in general. In that case, these projects are interesting. If these actions are done for climate change issues, they should be audited carefully, because some of them sometimes seem not very serious. On the other hand, in Spain, for example, Only 30% of the forest mass is managed “So it seems to make more sense to invest money in forests that already exist. Also, why invest in new plantations when the capacity of forests to regenerate naturally is high? And finally, it is not understood why in a plantation you can calculate the CO2 that will be absorbed but in a management project (thinning, clearing…) you cannot do the same and link carbon credits to management projects,” says the researcher.
Varied forests
Mature and diverse forests have advantages not only as a refuge for biodiversity, etc., but are also more resilient. This is stated in a recent study in Nature Climate Change (in which Creaf and CSIC participated) which explains that more diverse forests are less sensitive to rising temperatures and that biodiversity protects forests from premature leafing. “The study has shown that biodiverse forests have trees with deeper roots that can access nutrients and water at greater depths. On the other hand, a more biodiverse forest that generates more organic matter will be able to fix more carbon from the atmosphere. In fact, in these forests the ratio between carbon and nitrogen increases, so that plants, faced with a lack of nitrogen, allocate more carbon to root growth and slow down the leafing out,” concludes this recent publication.