What Is Biomass?

What is Biomass? That's a question often asked. Wikipedia calls it living or dead biological material and fecal matter. What this means is that it's plants, (trees, grasses, agricultural crops), and dung. It's renewable because it can be grown as required

Plants that form the most useful ingredients are grasses, hemp, corn, willow, sugar cane and oilseed rape. Timber is usually too slow growing to be used directly, but willow and poplar which grow fast are planted as crops. Waste from the lumber and furniture industries is also an important source.

Transporting biomass over distance is usually not economic unless it is made more dense and easy to handle. The best way to do this is to compress it into pellet form. This used to be done to produce animal feed, but pellets are increasingly being made for fuel.

Uses Of Biomass

Wood pellet producers compete in the market for sawdust and woodchips with the makers of particleboard, fibreboard and animal bedding. This competition for the raw material can lead to increased prices.

The residue of oilseed rape production has been compressed into logs that can be burned on an open fire.

Plastics can be made from biomass as well as from petroleum byproducts. Plastic that degrades in seawater has recently been made from biomass.

What Is Biomass And Biofuel?

Biofuels such as ethanol and biodiesel are made by fermenting biomass and by processing the oil from biomass. Biogas, (methane or CH4), is made by allowing biomass to rot and collecting the resulting gas. Gasifying is a process where the the raw material is brought to high temperatures without being allowed to ignite. The resulting gases are then collected.

A growing use of biomass is in co-firing with coal in power stations and in Sweden, some power stations are run purely on biomass.

Pelletising Biomass

To make pellets from biomass, ( see link at bottom of page), it first has to be ground down in a shredder or hammer mill to dimensions smaller than the finished diameter of the pellets. Pelletising wood is the easiest because when the material is extruded through the mill, high temperature allows the lignin in the wood to hold the pellet together. Wood pellets have a very low ash content.

For other raw materials such as the stems and leaves of maize, grasses and miscanthus, the process is more complex. Not only do these materials produce more ash, but it is more difficult to get the pellets to physically hold together.

For these ingredients, high temperatures are needed to soften them and binding agents such as paraffin oil, sugar, starch or lignin have to be added.

Benefits Of Biomass

The fossil fuels coal, gas and oil were biomass millions of years ago. They are not included in the current definition because the carbon locked up in them was long ago removed from the current environment. Burning these fuels now is a cause of global warming

Using biomass produced now is carbon neutral in that carbon released when this fuel is burnt is the same in quantity as the carbon absorbed when the biomass was growing. This produces much less harmful gas than allowing the biomass to rot when it gives off methane.

Biomass has virtually no sulphur content and so does not help to produce 'acid rain'.