Hemp, a plant grown centuries ago in England as a national duty, could help to restrict climate heating.
LONDON, 22 January, 2021 − There are high hopes that new technology and novel materials may save the world from the worst of the climate crisis. Fine. But don’t forget some of the old remedies − like hemp.
In the UK, hemp used to be a common crop which it was a patriotic duty to grow. In 1535 the English king, Henry the Eighth, required all farmers to sow a quarter of an acre (1,000 square metres) of hemp for every 60 acres they owned.
That was because hemp, one of the fastest-growing plants in the world, was recognised then for its value as a building material. Its reputation is now often tarnished by its relationship to cannabis, and it is usually called industrial hemp to distinguish it from its recreational and medicinal cousin.
Industrial hemp remains useful for many purposes, including construction, and not least as a substitute for concrete, the enormously carbon-intensive substance which is often the builders’ first choice.
“Hemp can be a lifesaver: it is naturally resistant to fire, providing greater protection against blazes overwhelming residential high-rise blocks”
The cement industry is one of the largest contributors to global warming, accounting for 5% of all carbon dioxide emissions. The reason it is so energy- and carbon-hungry is because of the extreme heat required to produce it. Turning out a tonne of cement requires about 400 pounds of coal and generates nearly a tonne of carbon. Global production is growing, and is expected to rise to 3.7-4.4 billion tonnes annually by mid-century.
The UK-based Rapid Transition Alliance (RTA) argues that humankind must undertake “widespread behaviour change to sustainable lifestyles … to live within planetary ecological boundaries and to limit global warming to below 1.5°C” (the more stringent limit set by the Paris Agreement on climate change). It believes the world’s profligate use of cement means it needs to rediscover the virtues of hemp.
The plant, it argues, could help to build low-carbon homes which would benefit the construction industry, employment, peoples’ health − and the environment. Hemp is also suitable not just for new buildings but for renovating and improving existing ones, something which will become increasingly important as countries seek to upgrade their housing stock enough to cut the need for heating and the carbon emissions it causes.
Hemp has already proved its worth to a large British industry. In 2006 Adnams’ brewery in eastern England built a huge carbon-neutral distribution centre. One visually striking feature is its arched roof covered in greenery, home to over half a million bees, with its own beekeeper.
Ideal for beer
The building relies on a construction material that could help future house-builders trying to provide for growing populations while also reducing carbon emissions. Its walls are built entirely from more than 90,000 lime and hemp blocks made of “hempcrete”, a lightweight mixture of lime and hemp stalks, making it the biggest building in the UK to use the material.
Hemp is light, good at regulating moisture and heat, and a good insulator. It’s also cheap, easy and fast to grow, and non-toxic to handle. The hemp construction lets Adnams save 50% on electricity and gas through its strong insulation qualities; it has a natural ability to maintain a constant cool temperature which is ideal for storing beer and other drinks.
Air locks and active airflow management are all that’s needed to keep the beer at the right temperature, without any artificial cooling or heating.
“By no means the least of the virtues of hemp is the fact that it can be a lifesaver: it is naturally resistant to mould and fire, reducing reliance on chemical fire retardants that have been linked to health problems and also providing greater protection against blazes overwhelming residential high-rise blocks.” When a fire broke out in Grenfell Tower, a 23-storey tower block in London in 2017, it killed 72 people. − Climate News Network
The Rapid Transition Alliance is coordinated by the New Weather Institute, the STEPS Centre at the Institute of Development Studies, and the School of Global Studies at the University of Sussex, UK. The Climate News Network is partnering with and supported by the Rapid Transition Alliance, and will be reporting regularly on its work. If you would like to see more stories of evidence-based hope for rapid transition, please sign up here.
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