Air

Greenhouse gases

The burning of wood waste and other plant biomass to produce heat and electricity results in emissions of carbon dioxide, a primary greenhouse gas. However, the cycle of growing and burning biomass recycles carbon dioxide from the atmosphere. For this reason, energy developers argue that power plants fueled by wood and agricultural wastes contribute little overall net impact to global climate change.

Some environmentalists say that the impact of biomass on greenhouse gases also depends on the practices used to harvest forest resources or grow energy crops. They argue that, if forests are harvested for fuel to generate electricity and are not replaced, atmospheric carbon dioxide will rise and global climate change could be accelerated.

In landfills, organic material decomposes and generates “landfill gas.” This gas is composed of carbon dioxide and methane, two greenhouse gases. Since each molecule of methane has 21 times the global warming potential of CO2, it is a potent greenhouse gas. When the methane gas is captured and burned to generate electricity or heat, it is converted to carbon dioxide, thereby reducing the net greenhouse gas impact.

Particulates

Particulate matter consists of solid or liquid particles that are released into the air and small enough to be inhaled. These include dust, soot, chemicals and other bits of material. Particulate matter is produced by natural sources (such as dust, volcanoes and forest fires) and human activities (such as mining, wood stoves, vehicle transportation and the burning of fossil fuels).

Particulate matter can reduce visibility and contribute to asthma, bronchitis and other respiratory problems. It also combines with nitrogen oxides and other emissions to form smog. Fine particulate can penetrate deep into the lungs and poses a greater risk to human health than coarse particulate.

The burning of biomass, like all combustion, releases particulate matter. Waste-to-energy facilities emit fine particulate matter when they burn wood and plant waste to generate electricity. These emissions can be controlled through emission control technologies, such as electrostatic precipitators, which remove most of this waste from power plant stacks.

Residential wood-burning stoves and fireplaces also release particulate matter. Modern, enclosed high efficiency fireplaces pollute less than traditional open fireplaces.