Developing pine biomass pellets to prevent fires

A research team from the University of Huelva has developed pellets made from residual pine biomass to prevent fires and increase the profitability of this plant material . This is the first study to analyze the physical and chemical characteristics of stone pine waste to produce a solid biofuel used to generate heat in boilers and stoves.

Although pellets were already being produced from various tree species, the researchers' proposal is the first to evaluate the density, moisture content, calorific value, and mechanical strength of residual stone pine biomass . Based on this data, they conclude that the final product has a high energy potential relative to its size , is efficient in combustion, emits a very low volume of polluting gases compared to fossil fuels, and its production is sustainable.

'Quality of the Pellets Obtained with Wood and Cutting Residues of Stone Pine', experts explain that stone pine biomass transformed into pellets has qualities such as its low moisture content, its bioavailability—it is an abundant resource in nature—and high density, meaning it contains a large amount of useful material in a relatively small volume. This facilitates storage and reduces transportation costs, as it makes better use of available space.

Advantages.
Thus, the development of these pellets offers two advantages: one environmental and the other economic . First, collecting biomass from forests and woodlands helps prevent forest fires, as it reduces the amount of potentially combustible material. Second, obtaining and selling stone pine pellets could cover up to 80% of the production and transportation costs of the biomass. “In the pine forests of Huelva alone, almost 1,000 kilograms of forest biomass per hectare could be sustainably obtained annually. With three hectares, the energy needs of a household could be met for a year,” explains Manuel Fernández, a researcher at the University of Huelva, .

To prevent or exacerbate forest fires , public institutions often remove large quantities of biomass from fire-prone areas. However, traditional methods have several drawbacks, such as the costs of collection and transport, the low energy density of biomass—meaning it contains a small amount of energy relative to its volume—and the quality and characteristics of the material. For example, some tree debris contains more water than usable material. This increases transport costs, since a large volume is moved, but little biomass is effective for generating energy or producing pellets. Furthermore, mixing different types of biomass can complicate processing, reduce energy efficiency, and hinder subsequent use. “For these reasons, transporting biomass over 100 kilometers is not cost-effective, environmentally sound, or energetically efficient. The pellets we propose aim to solve these three problems ,” adds Manuel Fernández.

High Density:
To develop these cylindrical pellets, scientists collected samples of bark, trunk, branches, and needles from stone pine trees in the vicinity of Doñana . They then analyzed, using traditional physical and chemical methods, the density, moisture content, calorific value, and mechanical strength of the pellets made from each part of the tree.

Thus, they concluded that barkless trunks and thicker branches are the best 'ingredients' for creating high-quality pellets , while small, thin branches and leaves have poorer physical qualities and, when burned, emit a greater amount of nitrogen, sulfur, and chlorine—gases that impact air pollution and human health. “Normally, biomass waste is shredded in the forest. We recommend transporting whole trunks and thick branches to make better use of the material. However, we do suggest shredding smaller branches and leaves on-site and spreading them on the forest floor to prevent them from becoming fuel and increasing the risk of forest fires,” says Manuel Fernández.

After determining the most useful parts of the tree, the experts transported the biomass to a pelletizing plant, where they ground the bark-free trunk and branches into sawdust, which was then densified . This process involved removing as much air and water as possible and compressing the material to produce pellets, which are elongated, cylindrical granules between 1 and 2 centimeters long. The scientists added that the sale of these pellets could cover between 30% and 80% of the costs of fire prevention work in the province of Huelva.

Meeting Energy Needs:
The next step for the Natural Environment Analysis and Planning research team will be to evaluate how a mixture of these stone pine pellets and other tree species performs. “If all forest and scrubland biomass were used sustainably, we could prevent the incidence of fires and, at the same time, meet the annual electricity and heating needs of 60% of Andalusian homes,” explains Manuel Fernández.