Solid Biomass supply for heat and power.
Solid biomass from forests, farms and cities provides a major energy source for heat and power generation, potentially accounting for a ﬁfth of global energy consumption by 2050 amid accelerated adoption of renewables. But wood and crop residues need to be collected from widely dispersed sites and stored for use at the optimal time, and at a cost-effective scale, in district-heating systems, power plants, and combined heat and power plants.
This technology brief from the International Renewable Energy Agency (IRENA) examines the multi-dimensional logistical challenges of establishing a steady supply chain for solid biomass.
In many places around the globe, in fact, the challenge has been met. Wood pellets for power generation, for example, with high energy density, low moisture content and sufficient durability, are shipped by sea from Southeast Asia to Japan and from Southwestern Europe to the Netherlands. Straw and food-crop residues are collected to provide village-level heat and power in India. In both cases, an effective supply chain depends of contracts to ensure feedstock at the required quality and cost.
Yet larger quantities of residues remain uncollected, whether from farms around the world or in developed countries with large-scale logging operations in managed forests.
But large quantities of available residues are not being collected. In Sweden and other countries with large managed forests, just a small share of the tree tops and branches left over from logging operations are collected. In Canada, large amounts of dead wood are abandoned in forests after being felled by storms or left standing in forests after insect infestations. On many farms around the world, crop residues not needed to feed or bed livestock are left in the field or burned to make room for the next planting. Typically, such residues are discarded because the cost of collecting and transporting them is greater than the market value they can fetch. Their enhanced use will therefore require more cost-effective logistical approaches or higher value-added applications.
In an increasingly globalised energy and commodity market, the standardisation of biomass feedstocks could serve as the key enabler for solid biomass trade. Feedstock pre-treatment, including drying and densiﬁcation, helps to meet quality standards.
Quality standards play a key role in expanding solid biomass markets. Different feedstocks have different physical and chemical characteristics that vary by region and season of the year. Often they start with too low an energy density for practical use or too high a moisture content for practical transport and storage. Standardisation of biomass feedstocks, to ensure quality at point of use, is therefore an important enabler of solid biomass trade in an increasingly globalised market. Feedstock pretreatment, with drying and densification, can help ensure quality standards are met.
Sustainability standards for solid biomass fuels are also likely to play a growing role. The wood pellet trade has generated interest in ensuring that pellets are sourced from the residues of lumber production that displace carbon emissions from fossil fuels without affecting land use, or from short-rotation wood crops that quickly compensate for combustion with carbon uptake. When wood residues are used, enough should be left in the forest to sustain biodiversity. When crop residues are used, enough should be left on the ground to maintain soil carbon and quality.
The wood pellet industry has made considerable progress in developing the logistics infrastructure for global biomass supply, including well-defined supply chains, contract provisions, quality standards and terms of trade. As concerns continue to mount over environmental degradation and climate change, sustainability standards are being developed and adopted to meet these concerns. However, considerable further logistical efforts will be required to harness the full increment of sustainable solid biomass supply for productive application in the heat and power sectors.
Source: IRENA technology brief