Energetic Potential of Biomass

Fields of grain, whose straw can be used for energy production.

Plants continuously convert solar radiation into chemical energy stored in biomass through photosynthesis. Large amounts of renewable biomass are therefore produced every year. An estimated 100 billion tonnes of biomass are produced globally each year, storing an amount of energy several times greater than total annual global energy consumption. Purpose-grown energy crops can provide an important source of biomass, alongside agricultural and forestry residues and organic waste from animal husbandry and other sectors.

7 pictures

7 pictures

Biomass Power Plants

Biomass power plants can use several conversion systems. Solid biomass is commonly burned in boilers to produce steam for a Rankine cycle with a steam turbine, while gaseous biofuels can be used in gas turbines or reciprocating combustion engines.

Biomass power plants can be fuelled by raw biomass or by processed biofuels. Their basic design can be similar to that of a conventional thermal power plant, with a steam-generating boiler and a steam turbine connected to an electric generator. The boiler and fuel-handling systems must be designed or adapted for the specific properties of biomass fuel. Replacing fossil fuels with sustainably sourced biomass can reduce fossil-carbon emissions, although the overall environmental benefits depend on the fuel source, supply chain and emission-control technology.

In addition to steam turbines, electric generators can be driven by reciprocating combustion engines using liquid or gaseous biofuels. Such units are often used for combined heat and power generation and can also provide flexible or peak-load generation. Their efficiency and emissions depend on the engine type and fuel used.

Alholmens Kraft in Pietarsaari, Finland, is a large combined heat and power plant with an electrical output of 265 MW. It also supplies about 60 MW of district heat and 100 MW of process steam and heat. At full load, the plant consumes around 800 m³ of fuel per hour, with biomass forming a substantial share of the fuel mix.

One of the world’s largest biomass-fired power stations is Drax Power Station in the United Kingdom, where four converted generating units provide about 2.6 GW of biomass-fired capacity.

Efficiency

A biogas plant using anaerobic digestion to convert organic biomass into biogas.

Combined heat and power (CHP) plants can achieve high overall fuel utilisation by producing electricity and useful heat at the same time. Depending on the fuel and plant size, CHP systems may use steam turbines, gas turbines or reciprocating engines. Systems that also provide useful cooling, for example for industrial processes or air conditioning, are known as trigeneration.

8 pictures

8 pictures