Is the Use of Peat in the Garden All Bad?

Recently the phrase ‘a renewable resource’ has appeared in connection with peat. To quote a stalwart of the U.K.’s horticulture industry, Peter Seabrook, “Peat is a reliable material and if we control water tables after harvest, it is a renewable resource”. It sounds at first as if black is being called white. Peat? Renewable? If that’s true then why all the fuss? Why can’t growers carry on potting up and potting on with it to their heart’s content? Because calling peat renewable is a bit like saying Christ is a Jew, strictly true but kind of missing the point.

Wood, Peat, Coal and Diamonds

If peat is renewable so is coal and so are diamonds even, but the timescales for renewable aren’t on a human scale. On a human scale a renewable fuel might be willow coppice at 1 to 5 years or wood, which takes between five and 100 (or more) years to renew. Peat is next in line at anything between 100 and 10 million years. Coal would be 20 to 325 million years and diamonds 660 to 3300 million years. So yes, renewable, but not in a hurry.

The UK Peat Industry

Peat has been a controversial item in horticulture for some time now. In the 1998 the British government set targets reduction in peat use in horticulture by 2010 and although the likely failure of the industry to meet the targets is being greeted with more of a shrug than an outcry, it shows the recognition that in the UK at least peat cannot continue to be used at the current rate. The industry struggles with the idea that it might not be green to use peat when it has served them so well to date. Nothing else quite lives up to its properties as a growing medium. Its clever leaf stems can hang onto water longer than other materials so that it requires watering less, when repeated watering would increase the risk of wet rot diseases this is an especially valuable quality. Peat’s structure is ideal for seedlings, providing space and air for them to push their delicate roots through.

Is Peat Sustainable?

‘Sustainable’ is another matter. Is the resource being used more quickly than it is being produced? On balance and worldwide the answer for peat (and coal and diamonds) is “yes”, it is disappearing quicker than it can be replaced. The situation varies wildly across different countries of the world however.

What is Peat?

Peat is made when layers of organic material decay more slowly than they accumulate. This happens where the ground is saturated so that oxygen cannot penetrate to help decomposition. In the northern hemisphere cooler temperatures slow the rate of decomposition and in tropical climates it’s the enormous volume of organic material that leads to accumulation in wet, swampy areas. Other materials have been preserved for centuries, including bodies such as the Tollund Man from Iron Age Denmark, and ‘bog butter’, thought to be an ancient method for preserving animal and dairy products!

Baltic States’ Peat Reserves

Siberia, Baltic and Scandinavian countries and Ireland have large peat reserves where it is commonly used as a fuel. It was decided in the eighties that using peat for fuel in Canada where there are extensive peat resources, did not compete with other cheap fuels such as coal, natural gas and oil so Canada became a leading international supplier of horticultural peat. In countries with large peat reserves the amount of peat used for fuel and in horticulture may well be sustainable especially if the bogs are managed after cutting.

Conservation and Regeneration

In Sweden a study at the University of Uppsala reported that if a bog is correctly re-wetted, the right conditions will allow peat forming plants to return to the area so that the peat can be renewed. Estimates are that it takes 3 to 5 years to sufficiently re-wet the area, several decades for the appropriate vegetation to re-establish and several centuries for peat to accumulate. Historically manual peat cutting was patchy – a bit at a time – and allowed regeneration naturally but modern machinery leaves no such uncut areas for potential regrowth.

The Cautionary Tale of Kalimantan

This kind of renewal project is extremely rare to date. Dried bog land, once the peat has been extracted, tends to be used for farmland or forestry. In this way many countries that had peat supplies have now lost their means of production as the bogs have gone. Both England and Ireland for instance have reportedly lost 94% of their original raised bogs. In Kalimantan, Southeast Asia, a combination of draining peatlands for forestry and then clearing the forest for agriculture by cutting and slash burning has had the disastrous effect of burning their massive peat reserves to ash. By comparison Sweden uses 0.1% of its 10 million hectares of peatlands a year for fuel and horticulture.

Peat bogs as Carbon Sinks

A study just published by the UK government concludes that peat use in horticulture should continue to be reduced but on the grounds of its value as a carbon sink (peatlands store huge amounts of carbon) and because it is ‘non-renewable’ rather than on the basis of greenhouse gas emissions. A study commissioned by the Finnish government argues for peat to be reclassified as a biomass fuel to distinguish it from fossil fuels (coal, oil) and biofuels (wood etc). Burning peat as fuel is ‘cleaner’ than coal and oil and it is more renewable than they are. Greenhouse gas analyses may come out in favour of its use as a fuel in this example but the increase in emissions from the peat fires of Southeast Asia may have contributed significantly to global warming.

The Future of Peat

Clearly there is some peat available as a resource globally. Whether it is harvested for fuel in the future remains to be seen but with the growing need to reduce the world’s dependence on fossil fuels it seems an obvious candidate. For this reason it would appear to be a good idea to wean horticulturalists off peat as their favourite growing medium where possible. In some cases, where plants really object to growing in anything else, the quantities required are likely to be small and it should be possible to carry on growing in it. An increase in understanding of the ecology of peatlands is leading to better management and the potential of sustainablility of this valuable resource. Should you buy ‘peat-free’ compost for your pots? The answer has to be yes.