Pellet fuels are critical to carbon emissions targets

There are many indicators that show that CO2 emissions from fossil fuels are causing rapid changes in environmental variables, and that the Earth system is not fully recovering the CO2 emitted. Not only is warming persistent, but in 2023 we may cross a tipping point, leading to more rapid change with increased variability (more extreme highs and lows). If the future is what we hope it will be, action is needed now.
Seeking a just, orderly, and reasonable solution
Today's socio-economic system is based on the fact that we get our energy from fossil fuels. So what we're looking for is a "plug-in" alternative that can continue to power the infrastructure we rely on while minimizing disruption.
In the electricity, heat and transport sectors, so-called "drop-off" solutions have been deployed. High-energy-density liquid fuels made from renewable feedstocks are being used more and more and their costs are falling. The use of ammonia and hydrogen (produced from renewable sources) as non-carbon energy carriers will be part of the transition. In many EU countries and North America, heating from sustainably sourced wood chips and wood pellets is commonplace.
However, the electricity generated by wind and solar cannot be considered a one-time energy source entirely because it is variable. As a result, no matter how many MW is deployed, sometimes it will generate less electricity than the grid needs.
Over the next few decades, energy storage solutions are likely to be developed and deployed on a scale sufficient to buffer intermittent and variable supply and keep the grid stable for most, if not all, of the time. But for at least the next few decades, to make the transition to a decarbonized future as seamless as possible, the grid will need on-demand and load-tracking, low-carbon generation.
The use of pellet fuels produced from constantly updated biomass solves part of the problem. Existing coal-fired power stations can be retrofitted at a relatively low cost and with less downtime, and coal can be replaced with pellet fuels produced from energy that is constantly being renewed (rather than depleted). The result is that renewable electricity can be produced on demand.
   

Pellet fuels: an energy-dense energy storage solution
It is a mistake to think that forests will always be a net absorber of carbon dioxide. They will always reach saturation. But if managed properly, they can be used continuously without reducing the amount of net carbon they store. If the biomass is not depleted over time, no excess carbon dioxide is produced and therefore does not accumulate in the atmosphere. In the case of forest biomass, the amount of carbon dioxide released by any wood burned is less than or equal to the amount of carbon dioxide captured, if the amount of wood in it is not depleted (i.e., the removal rate of wood never exceeds the growth rate). This logic only works if the resources are constantly updated. Sustainability is an absolute necessity for generating electricity using pellet fuels as an alternative to coal.
The vast majority of primary harvesting of woody biomass for the forest products industry is not used for the production of pellet fuel. The main users are sawmills (wood, flooring, furniture, etc.) and pulp and paper mills (printing paper, cartons, toilet paper, etc.). These mills have been in operation for more than a century in some places because they harvest less than or equal the amount of timber grown in the surrounding forests each year. With proper maintenance, these plants can essentially run forever. Well-managed pellet plants also benefit from the same forest resource management.
Providing a seamless, low-carbon input to the grid, either base load or load tracking, and can be used on demand, so what is the decades-long transformation strategy?
We already have large-scale energy storage that can be part of the solution. Biomass energy cycles to capture and store solar energy. Forests are actually the world's largest solar cells. Every year, approximately 5.7 x 10^24 joules of solar energy hits the Earth's surface. Solar energy is an important part of the Earth's ecosystem. Plants and photosynthetic organisms use this energy to convert large amounts of carbon dioxide into glucose. The chemical process of plant growth converts glucose into other sugars (hemicellulose), cellulose, lignin, and other plant matter. Every year, solar energy and photosynthesis convert billions of metric tons of carbon dioxide and water into plant matter and produce oxygen as a by-product.

Part of the plant is the trees. While some forests are not and should not be used to supply the forest products industry, millions of hectares of forests are managed and cultivated to continuously produce logs needed for timber, furniture, and many other products in everyday life. These forests also produce wood chips, which are used to make paper, packaging, paper towels, and various engineered wood products. Some of the by-products of sawmills and the rest of the trees are not suitable for higher value use and may go into pellet mills to produce solid fuels, as well as plants to produce renewable liquid fuels from cellulosic feedstocks.
These managed forests are in fact forest farms. Each plot of these tree farms goes through a cyclical phase of regeneration, growth to maturity and harvesting. But in general, as long as the rate of felling does not exceed the rate of growth, the total amount of wood (and therefore the carbon stored therefrom) will not fall. The average growth rate of forests around the world is about 12 tonnes per hectare per year. Less so in the northern regions, in some tropical regions with fast-growing tree species, more than 20 tonnes per hectare per year.
Forests cover about 31 per cent of the world's land area, or about 4 billion hectares. Assuming an average growth rate of 12 tonnes per hectare per year and an average energy content of about 86.4 gigajoules (GJ) per tonne (based on wood with a moisture content of 50%), the energy reserves of the world's forests are about 415 billion GJ, or 115 million GWh per year.
It is estimated that the total generation of wind and solar power in 2022 is around 3.5 million GWh. Forests capture and store about 33 times more energy each year than all solar and wind combined. In addition, almost all of the electricity generated by solar panels and wind turbines is consumed during production. Without storage, solar and wind energy cannot be dispatched, while solar energy captured by the world's forests is stored.
Clearly, according to the Food and Agriculture Organization of the United Nations, only a fraction of the world's forests are used to supply the forest products industry – about 30 percent. Based on an estimate of how much of the total primary harvest in North America becomes pellets (4.5%), and using this ratio to estimate the global GWh that could potentially be used for pellet fuels, more than 1.55 million GWh of forest energy storage could be transferred to pellet fuels each year without depleting the carbon stocks in forests and forests.
BloombergNEF predicts that by 2030, there will be about 1,880GWh of long-term energy storage. Based on the forests already managed for the production of raw materials such as wood and paper, and using only 4.5% of the material to produce pellet fuels, pellet fuels today have the potential to provide 826 times more energy stored per year than all energy storage solutions projected by 2030. If bioenergy carbon capture and storage (BECCS) is included in the analysis, not only can the stored energy be used to help keep the grid stable, but the stored carbon can be permanently removed from the atmosphere.
The beginning of the end of the fossil fuel era
There is already a pathway in place to support decarbonization goals, and it can be deployed now. In 2022, the global pellet fuel supply chain stored energy every day in the form of carbon-friendly pellet fuel, equivalent to a Panamax ship (about 65,000 tons).
On the demand side, large utility power stations have successfully completed the "biotransformation". For them, coal is a thing of the past; Dispatchable or baseload generation is not. An orderly transition from today to an ideal future should include policies that support the responsible use of solid fuels obtained from stored solar energy to regenerate biomass. There are still far from enough renewable biomass energy to replace all of the coal being used, but they are enough to make a significant impact.