Biomass... A 21st Century Fuel?

The thing about gas and oil is that they are so convenient. You buy a boiler, the plumber knows how to fit it, then you set the timer and forget about it. Once a year, if you remember, you should get it serviced but you don’t have to do or think about anything else. We have even got a little more used to the high fuel prices. Five years ago fuel oil was less than 20p per litre. It is now more than 55p — a rise of 175%. If we had known that was coming five years ago we would have done something about it then.

There is no reason to suppose that prices won’t spike again soon, so perhaps now is the time to do something. And maybe that something is switching to biomass.

What is Biomass?

Biomass is a generic term that includes all plant material that can be burned. So it includes wood but also things such as straw, rape-seed pellet, grain and flax. Usually it means wood as either log, chip or pellet.

Modern log burners often need logs cut to a certain size. Chip is usually the waste from forestry work, that is chipped to a specific size to enable better drying and easier handling. Pellet is wood dust, also often waste wood forestry waste, sawdust from joinery works, old pallets and the like – formed under pressure to 6mm- or 8mm-diameter pellets.

Wood pellet is by far the most common biomass fuel as it offers the best calorific value (the amount of heat for each unit of fuel), is lightest by volume (because it is the driest) and is the easiest to handle.

What this amounts to is a huge range of types and styles of biomass stoves and boilers. From log-burning stoves that have to be stoked every couple of hours to fully automated wood-pellet boilers that are almost as convenient as gas boilers.

Cost of Biomass Fuel

There are two potential motives to choosing a heating fuel: low CO2 emissions and cost saving. Happily biomass gives both.

Biomass is a carbon-neutral fuel. It emits the same amount of CO2 when it is burnt as it absorbed when it grew, so the net effect on the planet is neutral. Wood pellet is a manufactured product and as such it has embodied energy and CO2 — the energy and CO2 used in its harvesting, manufacture and transport. The National Energy Foundation estimates that the embodied CO2 in wood pellet is just 1.62% of that in fossil fuel.

The cost of biomass fuel varies with the type and quantity purchased — from £35 per tonne for logs bought locally to £210 per tonne for good-quality pellets bought in small quantities in 10kg bags. See the first table below for its typical cost as a comparison to traditional fuels.

It is worth noting that the price of bulk wood pellet in 2005 was 2.7p per kWh — a rise of just 7.4% in three years. Also, the rise in pellet prices is slowing (even reversing in some areas) as more manufacturers enter the market.

As with any heating system, deciding on the fuel is the first step. In this case it will determine the type of boiler. It is also important to secure a source of supply, as there is no national network of biomass fuel as there is with gas and oil. The National Energy Foundation website at nef.org.uk provides a lists of fuel suppliers.

Boiler Types and Costs

The range of types of burners is huge; from log-burning stoves to fully automated, industrial- size wood-chip or pellet boilers. To decide which boiler is right for you there are two issues to consider: the type or fuel you want to use and the level of desired automation.

The second table below shows the sort of price variation for stoves and boilers suitable for a typical four bedroom house.

A system that is intended to provide central heating and hot water will also need a large hotwater storage tank, at least 300 litres capacity. This is because biomass boilers are most efficient when they are running at their optimum combustion temperature of 1,200°C, and it takes time to get to that. So normal operation is to have one or two ‘burns’ each day and store the energy in the hot-water storage tank for use during the day. Controls are the same as for a gas or oil boiler with thermostats controlling room temperature. In this case the thermostat is connected to the hot-water tank rather than the boiler.

The cost above may seem high but compare it to a typical oil-boiler installation. For a new condensing boiler, oil storage tank, hot-water cylinder, fuel and electrical connection, there won’t be much change from £4,500. A similar, good-quality wood-pellet system would cost around £7,800. Less £1,500 grant and the price drops to £6,300 — just £1,800 more than oil.

Is Biomass Really a 21st Century Fuel?

To answer this we can do no better than look at major supplier Euroheat. The company has been in business since 1992 and is now a multi-million pound enterprise supplying all forms of biomass equipment.

The MD, Michael Barber-Starkey, says, “The barrier to biomass boilers becoming a massmarket product is still capital cost.” But in the last few years the company has seen a 25% growth in stoves and a staggering 70% growth in biomass boilers. “It is simple economics, explains Barber-Starkey. “If you have a big house to heat you don’t want to look forward to the oil price rises we have had in the last few years”.

It is clear Euroheat believes that biomass is the fuel for now and the future. The company claims that rising oil prices are driving up sales of wood-pellet boilers, which in turn will drive down capital cost and so making them mass market in five years. With the price hikes we have seen this summer, who can argue?

Inside a Biomass Boiler

The inner workings of a Baxi Multi Heat wood-pellet boiler. It uses an auger to transport the fuel from the hopper at the back of the unit to the combustion chamber, where it is mixed with precise volumes of air delivered via a modulating fan. This ensures maximum combustion efficiency is maintained at all times. See baxi.co.uk for more information

Grants

The Low Carbon Buildings Programme(lowcarbonbuildings.org.uk) offers grants to support the installation of biomass systems. A wood stove will attract a grant of £600 or 20%, whichever is less, and a boiler £1,500 or 30%. In Scotland the grant rises to 30% of the cost. And they all attract VAT at 5%.

Further Reading:

• The Death of Central Heating?
• Biomass
• Wood Burning Stoves: A Buyer's Guide