Advantages over untreated biomass
Producers of power and heat are increasingly interested in using biomass as a fuel. However, to date, biomass has suffered from three major drawbacks that have prevented its fast and large-scale use in power and heat generation:
- Biomass has high transport and storage costs, due to its low energy density and the moisture-absorbing nature of the product;
- Biomass has sub-optimal physical properties for co-firing, such as the tendency to absorb moisture, as well as its grinding and burning characteristics. To address these issues, sizeable investments are required in a power and/heat plant, if such a plant is to (co-)fire biomass; and,
- Existing boilers in power and heat plants can only co-fire a limited amount of biomass with coal. The fact that only a limited volume of biomass can be co-fired despite the sizeable investments in the co-firing capacity of the plant adds to the total costs of sustainable power and heat.
Torrefaction lowers the transport costs of biomass
Through torrefaction and compacting, the volumetric caloric density (GJ/m3) of biomass increases by approximately 70%. This leads to savings in the transport, storage and handling of biomass between source and end-user location.
Torrefaction lowers the costs of using biomass in existing power plants
By using torrefied biomass, utility companies avoid additional capital expenditure in existing power plants, which would otherwise be needed to process ordinary biomass so as to co-fire it with coal. Untreated biomass, such as wood pellets, require extensive additional capital expenditure for landing (quay facilities), storage (silos, given that wood pellets cannot be stored on a yard, as opposed to coal which is stored on a coal yard), feeder lines to the mills, as well as milling capacity. Torrefied biomass, however, can be processed in a similar manner as coal. Compared to wood pellets, Topell Energy expects torrefied biomass to save its customers approximately € 1 per GJ on averted investment costs.
High co-firing rates are possible with torrefied biomass
The coal-like characteristics of torrefied biomass make it possible to blend it with coal in much higher proportions than are achievable with untreated biomass, such as wood pellets. Wood pellets are typically co-fired with coal at a rate of approximately 5 to 10%, whereas torrefied biomass is expected to be achieve co-firing rates in the range of 50 to 80%.