Is a biomass boiler right for your home?

What is a biomass boiler?

Biomass energy derives from living organisms, such as plants, trees and animals. Biomass sources can be burnt to provide heat or converted into fuel. On the eve of the Cop26 summit, Prince Charles famously revealed he runs his Aston Martin on “surplus English white cheese and whey from the cheese process.” His car was converted to run on a high blend of bioethanol made from cheese and wine wastes. Charles is not alone. London buses and some HGV vehicles are also powered by biofuel which - if not using cheese and wine – use other waste products, such as coffee grounds and biogas from cows’ manure.

The most widely used biomass source is wood. Biomass boilers that we use to heat our homes and provide hot water typically burn wood pellets or logs. While a stove will warm a single room and may be fitted with a back boiler to provide water heating as well, a boiler can heat radiators for the whole house as well as hot water. Both wood pellet and log boilers will require a hot water cylinder.

ADVANTAGES

Renewable

Biomass is considered a renewable source of energy because, unlike coal which takes millions of years to form, wood can relatively easily be replaced by planting new trees.

Wood pellets are typically made from compacted sawdust and other by-products of logging or milling lumber for construction materials or furniture. Some softwoods, like poplar trees, may be grown specifically for pellets.

Reduces dependence on fossil fuel

Fossil fuels, such as coal and oil, are not only limited in supply but burning them releases large amounts of carbon dioxide into the atmosphere, harmful to the Earth’s ozone later. Biomass is an alternative, renewable energy source that is unlikely ever to run out.

Low carbon option

Burning wood is said to be carbon neutral because it releases about the same amount of carbon dioxide into the atmosphere as was absorbed in the years the trees grew by natural photosynthesis. The balance of this equation may be tipped by carbon emissions from manufacture and transportation.

If the wood is sourced locally, however, emissions will still be lower than from fossil fuels.  According to Greenmatch, replacing a coal or electric heating system with a biomass boiler can reduce your carbon footprint by up to 9.5 tons per year.

Renewable Heat Incentive

Biomass boiler systems qualify for the Renewable Heat Incentive (RHI), a government-run scheme aimed at encouraging people to invest in renewable energy systems. Under the RHI scheme, homeowners are eligible for quarterly payments over seven years. The payments help to recoup some of the upfront cost of buying a wood pellet boiler or stove.  To qualify, the biomass boiler must comply with air quality requirements and be installed by a registered plumber.

Cheaper to run

Biomass boilers are often cheaper to run than conventional oil and gas-fuelled boilers through the capital cost is significantly more. What’s more, the price of wood pellets aren’t subject to global oil price fluctuations, so you won’t see a sudden hike in your fuel bills.

DISADVANTAGES

Space requirements

Biomass boilers need more space than a conventional gas or oil boiler but should fit in most utility rooms. A log boiler is, however, a bigger beast and may need a dedicated plant room. In addition to the boiler, you need somewhere to store the fuel, such as a wood store, garage or storage room. Wood pellets and logs need to be kept dry or they won’t burn efficiently. The store needs to be handy for feeding the boiler as well as accessible for deliveries. Pellets are available bagged – often 10kg or 15kg bags delivered by the pallet load.

Involves more work

Biomass boilers require a constant supply of logs or pellets. Most pellet boilers have automatic fuel feeders, known as hoppers, which refill them at regular intervals.  Log-burning stoves and boilers must be re-fuelled by hand and so require more work. Cleaning is another issue to consider. Some are self-cleaning, others partially so and some are entirely manual. Log boilers are likely to need monthly cleaning. Wood pellet boilers may only need ash removal once or twice a year. Requirements vary. All boilers need annual servicing.

A lot of logs will be needed to heat a whole house but if you have a good local supply, they can be cheaper than pellets. Checking for availability of suppliers before buying a biomass boiler is a good idea as not all areas are well served.

Isn’t squeaky clean

While there is an argument for carbon neutrality, biomass isn’t as clean as wind power or solar. In addition to the release of carbon dioxide, burning wood results in the release of other harmful gases such as carbon monoxide and nitrous oxides which all contribute to air pollution.

You will need a flue that meets the regulations for wood-burning appliances, such as a new, insulated stainless steel flue pipe. Existing chimneys normally need lining to make them safe and legal.

Deforestation

Biomass sources are renewable, but woodland must be responsibly managed to ensure resources don’t become depleted faster than they are replaced. Otherwise, there is a risk of deforestation. There are possible biodiversity concerns too because wildlife and habitats face disruption from logging not immediately solved by planting saplings. 

Wood pellet boilers and biomass stoves can be an eco-friendly and, to some extent, cost-effective option for bigger properties, particularly with access to their own woodland/fuel supply. It’s not likely to be a practical choice for every household due to the space requirements and high upfront costs. When weighing up the pros and cons, take into account the Renewable Heat Incentive payments plus cheaper fuel prices.

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