The Carbon Footprint of Gardening

, written by Jeremy Dore gb flag

Leaf footprint

The media often gives the impression that all gardening benefits the environment. Surely gardens are always good as plants absorb carbon dioxide (CO2) and give out oxygen, reducing our net carbon emissions? Surprisingly, it’s not always that simple. There are many inputs to modern gardening methods that need to be questioned as they release significant quantities of greenhouse gases:

  • Fertilizer: Almost all synthetic fertilizers that contain nitrogen will have been produced using the Haber Bosch process. This relies on converting the methane from natural gas into hydrogen first and the resulting by-product is CO2 making commercial fertilizer production a large producer of greenhouse gases. Manure is not much better as composting it releases methane which is itself a very potent greenhouse gas and some people calculate that the resulting carbon emissions are worse than for synthetic fertilizers.
  • Peat: Natural peat bogs are one of the earth’s best carbon sinks – they absorb CO2 from the atmosphere and lock it away. Buying potting soil that contains peat has a negative carbon impact because it removes part of the earth’s ability to absorb greenhouse gases. Amazingly nearly half of all potting soil sold in the UK still contains peat so if it doesn’t say peat-free on the label it probably isn’t!
  • Heat: Heating greenhouses is a very inefficient process. There is no double-glazing and they’re draughty because good ventilation is required for plants. Unless you’re using electricity from a wind-turbine to power an electric heater there will be a considerable carbon footprint.
  • Water: Food gardening requires large amounts of water especially during hot summers. When that comes from treated drinking water supplies the carbon footprint can be significant. A hosepipe can use 1000 liters per hour and the energy that went into treating and supplying that water is equivalent to leaving a 60W light bulb (or 5 low-energy light bulbs) running for the same period of time.
  • Non-renewable Resources: Gardening stores and gardening supply companies often promote their green credentials yet their bottom line is nearly always profit and persuading us to buy ever increasing amounts of hard goods. Everything they sell requires energy to produce, adding to your garden’s carbon footprint.
  • Transportation: Although growing food cuts out all the food miles that come from the food superhighway that supplies our grocery stores there are still many garden products that are shipped around the world.

Once you take all these into account it’s easy to see why the kind of easy gardening encouraged by gardening stores could actually end up contributing to a higher carbon footprint, adding to the problem of climate change.

Pallet composter

Good-for-the-World Gardening

Plants are so good and so central to our world’s natural balances that in many cases we simply need to live ‘lighter’ on the earth. Here are some possible solutions:

    Fertilize with Compost and Green Manures (cover crops): There is now ample evidence that using good organic gardening techniques produces crops that are at least as good as non-organic and much better for our health and world. Composting everything you can reduces the methane emissions that would come from sending it to landfill (it’s estimated that about 25% of all landfill waste in England could have been composted) and increases your gardens growth, a win-win situation. However, to keep methane emissions low, the composting needs to be well aerated so techniques such as hot composting where the pile is regularly turned to mix in air are preferable. There’s some good advice on how to get the right mix for hot composting on the Recycle Now website.
  1. Reduce Reliance on Manure: For most food crops manure needs to be well composted before use to eliminate pathogens but this process is what creates methane. Apart from the release of greenhouse gases there are other problems with manure such as aminopyralid herbicides so it’s best to substitute compost and green manures where possible.
  2. Avoid Peat: It isn’t easy to find high-quality compost for seeds and young plants since many peat free composts come from composted wood chippings and are too coarse. One solution I have tried is coir-based compost such as Fertile Fibre and I have had excellent results with this for several years. Coir is a waste product from the processing of coconut fibre and it is shipped across the world to reach us. However, this shipping is low on the scale of transport-produced CO2 and the resulting compost is so much better than alternatives I have tried that I think it’s worthwhile.
  3. Supplement Light not Heat: It’s much more efficient to start seedlings inside a heated house with full-spectrum grow-lights than to heat a light but draughty greenhouse. I have now taken to leaving my greenhouse empty over winter and raising seedlings with grow-lights in a bedroom (warm air rises in the house so it’s naturally warm).
  4. Use Grey Water: With sensible precautions water from roofs, sinks and baths can be used around the garden rather than treated drinking water.
  5. Reduce, Reuse, Recycle: For some excellent tips see our article on Recycling in the Garden where many of our readers have commented about how they use other people’s cast-offs in the garden.
Grey water

A lot of this has been common practice amongst organic gardeners for some time now. It seems to me that the real challenge is going to be spreading this to the general public. We need people to move away from commercial quick-fix gardening to an awareness of how growing your own organic food can help offset the carbon footprint of our lives. This is what governments really need to encourage if they want a significant reduction in our carbon footprint.

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Comments

 
"Wow - a seriously excellent article, Jeremy - thank you for sharing that. A great read, opportunities for further reading and a fantastic boost in the garden, where it counts. I've sent the link to this article to four of my best gardening buddies."
Kevin on Friday 17 December 2010
"Jeremy my Moriga Tree is suffering from yellowing of the leaves,can you tell me what might cause this and what is the organic remedy for this problem.I doubt it's the constant rain in my country Philippines for it's rainy season out here"
Jovenal on Thursday 30 December 2010
"Jovenal, the Moringa tree usually does well without much fertilisation. Yellowing leaves can also be caused by pests such as mites as mentioned in this document: http://www.avrdc.org/LC/indigenous/moringa.pdf. I would recommend a very close inspection to see if it is mites that are causing the yellowing (in which case seek advise from your local agricultural office about the best organic remedy). If it just needs fertilisation then a thick mulch of compost for several feet around the tree base should help as the rains will carry the nutrients to the roots."
Jeremy Dore on Thursday 30 December 2010
"You forgot to mention all the books that we all purchase as start on our journey to self-sufficiency in relationship to growing fruit and vegetables? Afraid at the moment I have to use manure, my allotment site is waterlogged most of the year from October onwards until the growing season starts. The soil level is too low, so am using the no dig method to raise it and the use of manure is the only way I can get organic matter into the site. The soil is clay type, pH is relatively neutral. Growing some serious crops this year which is my second growing season, having got the site in November 2009. Your planting planner is coming in very useful as it saves on paper and other resources, when you change your mind on what is going where. In relationship to my carbon footprint, not sure how high that would be. Neither of us drives, so we use public transport, the allotment is 3 miles from the house so I have use the bus. As for transporting large items wood for construction or in this case (soon to be erected) a poly-tunnel will done by a friends car or a van. I re-use all the meat trays form sausages, yoghurt/cream pots and toilet rolls for growing seedlings in, either transplanting them directly in the soil or potting them on. Glad to know that I am on the right track with the green manure, as there is an area in which I will grow Lucernce and there is a comfrey area already, well contained in both cases. Having my degree in Wildlife and Practical Conservation meant I had already considered many of these factors, something I think/thought most people never even thought of."
Steve on Saturday 29 January 2011
"This article raises some important issues and reminds us to consider the costs and alternatives, as we should when contemplating any action. I think there's a logical flaw in the admonition not to use manure as fertilizer, however. Manure is a waste product of raising animals, usually for food. It is not produced for the purpose of gardening, and won't "go away" if we all completely stop using it today. It's going to be there, and it's going to break down, producing its greenhouse gases, whether or not we capture its nutrients for food use. I believe that if you have a local source for manure (a heavy, wet thing to transport long distances), and can avoid the plastic packaging of bagged manure from the garden center, that it's perfectly sustainable and sensible to use it as fertilizer. Animal manure is an important part of a food raising ecosystem- see Joel Salatin's work for more. "
Heather on Friday 4 February 2011
"ALL GARDNERS SHOULD LOOK INTO USING BIOCHAR IN THEIR HOME GARDENS...LOCKS UP BAD GASSES FOR A LONG TIME...BUT THE REAL BENEFIT IS GROWING BETTER CROPS AND USING LESS FERTILIZER AND LESS WATER....A WINNER"
ROY WILLMOND on Wednesday 13 April 2011
"Where can you affordably get biochar from in the UK? Or how do you go about making your own charcoal? In either your back garden or on an allotment (which in most built up areas are smokeless zones)? What is the application rate/sq ft or M? We could all benefit from using the Terra Preta method of gardening supposed to up yields by as much 300%. It was used by the Meso-American Indians in Central and Southern America. By using bio-char it meant that large communities/cities could be supported from a rainforest when the soil is treated in this method. They went about it in a different way controlled slash and burn. I suspect they had several growing patches used them for a number of years, then moved to the next one, allowing the first lot to recover, until that time frame had expired on the second plots. Then moved back to first plots with their slash and burn, thus incorporating the biochar in their soil. They only knew it was really fertile recent research is starting to show just how fertile. The carbon (in the form of biochar)locks or unlocks key nutrients hence the increased harvest."
Steve Calver on Wednesday 13 April 2011
"Weeding your garden is not very eco freindly!"
bob on Tuesday 19 April 2011
"Bob In what way is weeding not friendly in a garden that is designed either for flowers or for growing vegetables. I know that weeds are plants growing in the wrong space are you suggesting that we should leave a space for weeds in our gardens? I can see where you are coming from it helps biodiversity and thence predation of undesirable pests. It is a constant battle with weeds at my allotment, you never get them all just most of them and same applies to slugs as well."
Steve Calver on Tuesday 19 April 2011
"Has anyone tried cotton burr compost, arguably the best compost available? I am working it in as I replant summer crop beds with winter plants and direct seeding. "
Pat on Sunday 10 July 2011
"Wow! very interesting. "
ilmanvaihtokanavien puhdistus on Wednesday 19 June 2013

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