Biomass Feasibility Project Final Report - Xcel Energy

CHAPTER IV : BIOMASS HARVESTING,
PROCESSING AND TRANSPORTATION
The next step after determining which biomass fuels are appropriate to the project is to decide
the best way to handle them between the field and the power plant. Biomass has to be:
• harvested without contamination
• collected
• processed (including drying, size reduction, and/or densification),
• transported to the power plant
• stored
Except for the obvious first step – harvesting – other steps might occur in various orders and
places, depending on cost factors and logistics. Storage, for example, might occur at the
harvest site, collection site, plant site, or all of the above. The same is true of processing. In order
to reduce transportation costs, biomass may be dried and/or size-reduced at the farm or
collection point and then further processed into fuel at the power plant.
Since so much of the cost of biomass fuel stems from its harvesting, collecting, storing, processing
and transporting, the financial success of a project may rely as much on the thought and
ingenuity that go into these steps as it does on the generation technology itself. Some schemes
go so far as to envision small, portable gasifiers installed on flatbed trucks going from farm to
farm, collecting biomass, reducing it to gases and char, and delivering those fuels to a power
plant – providing in one fell swoop all intermediate steps but harvesting. Whatever the scenario,
efficient handling of low-density, low BTU material like biomass is key to the economic success of
a biomass power project.
HARVESTING AGRICULTURAL BIOMASS
Growers have to make a paradigm shift to sell biomass fuel. They must come to see residues,
like straw and corn stover, as valuable commodities due to their energy content and treat them
as such. If stover, for example, comes in contact with the soil, its usefulness as fuel is diminished.
Up until now, farmers have left stover in the field. Recently, however, manufacturers of
harvesting machinery have begun to develop new models that capture these by-products with
the same care as crops. Those machines will allow growers to sell residues for production of
cellulosic ethanol as well as biomass power generation. Once those markets become
established, it won’t take long for growers or contract harvesters to adopt the new paradigm.
HARVESTING TIMBER
Loggers also will have to view residues as a valuable part of their harvest. Because of its density
and high BTU content, wood is the easiest form of biomass to transport and burn in a power
plant. But as we’ll see later, if silica, or grit, is delivered with the wood, it will slag, or cake, on
boiler surfaces and cause damage. Some plants using wood fuel have had to reject deliveries
of woody residues because of contamination. To sell into energy markets loggers will have to
learn to keep slash – limbs, leaves and tops – off the ground.
Page 40
Identifying Effective Biomass Strategies:
Quantifying Minnesota’s Resources and Evaluating Future Opportunities