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Health & Nutrition
The Greenhouse Effect - Environmental Issues
Is it sustainable, people ask, to grow tomatoes in glasshouses in northern Europe, using precious fossil fuel to heat them, when they can be grown in the sunshine of southern Europe and imported here? An apparently simple question, but with a rather more complicated answer.
British tomato growers can claim outstanding achievements in environmental protection. These achievements are based on:
People in glasshouses Most of our imported tomatoes come from Spain and the Canary Islands, traditionally through the winter, but with the season being increasingly extended through the rest of the year. The adoption of long-life varieties, to withstand the transport involved, has played a major part in this development. Even in Spain, the sun does not always shine and most crops are now grown in greenhouses covered with polythene. The polythene has to be replaced every three years or so and it can take up to five times the area of polythene greenhouses to produce the same quantity of tomatoes as in British glasshouses in a year. This means that in the 25 year life of a glasshouse (some are still being used after 50 years!) it could take 40 times the area of polythene to produce the same weight of tomatoes. What is polythene made from, how long does it last and what happens to it after use? The same sort of factors apply to the use of water. The weather in the spring of 2005 was unusually cold in southern Europe and north African countries such as Morocco. Salad crops were badly affected by this and tomato fruit quality was very poor. The weather in the early spring of 2006 was also cold, though not quite as severe, and crops were again affected. Supply from British glasshouses is much more secure. Many tomato crops in southern Europe are now commonly infected by diseases, such as Tomato Yellow Leaf Curl virus (TYLC) and Pepino Mosaic virus. TYLC is transmitted, mosquito like, by the tobacco whitefly (Bemisia tabaci) moving from plant to plant when feeding. The tobacco whitefly has become a serious problem because there is a much greater reliance on pesticides in southern Europe than in Britain. It has become resistant to many of these pesticides, which no longer give good control as a result. So far we have managed to keep Bemisia out of the UK and do not have its associated virus to contend with. We have also taken much more stringent precautions against Pepino Mosaic virus than in other European countries.
Energy Use During this period the majority of the production area was converted to use natural gas for glasshouse heating, resulting in less of the sulphur emissions which would come from burning oil or coal. Carbon dioxide can also be extracted from the clean exhaust gases when burning gas, to enrich the glasshouse atmosphere with CO2. This gives big production benefits as well as further reducing CO2 emissions.
Combined Heat and Power (CHP) The UK government is committed to stimulating CHP development as one of the largest potential contributors to reduced greenhouse gas emissions and environmental protection. We estimate that a quarter of the UK tomato production area is now equipped with CHP facilities. This figure could rise further but one current problem is in the imbalance between the high costs of gas or oil and the price of electricity. If all of the UK tomato area were to be serviced by CHP units, at a typical electricity generating capacity of 1 megawatt per hectare of glasshouse, the industry could achieve around 3-5% of the Government's national year 2010 target for CHP power generation on its own. CO2 uptake by British tomato crops is estimated to be 20-25,000 tonnes per year. This means that British tomato growers have reduced CO2 emissions by a total of around one quarter of a million tonnes in the past 15 years. How many other industries could claim anything like this?
Pesticide Use British tomato growers were the first to use natural enemies of pests, rather than chemical sprays, as a way to control them. These natural enemies are raised and supplied to growers by specialist 'bug breeders'. Each pest has its own predator or parasite, sometimes more than one, which lives on it, and growers have had to become highly skilled at monitoring their crops to pick up a pest attack at an early stage. They also have to maintain a balance between the ‘bug busters’ introduced to the crop and the pests. This simple system is very effective. Pests have become resistant to many insecticides. This means they no longer work. Another bonus is that consumers and glasshouse staff no longer come into contact with pesticides and neither do the two million bumblebees which are used by all British tomato growers to pollinate their crops. Bees don’t like pesticides either! The other reason British tomato growers can make this approach work is that they have sophisticated glasshouses in which the environment can be precisely controlled. This also reduces the risk of tomato plants becoming diseased. For example, potato blight can be a serious problem, especially during wet summers. It does not effect commercial British tomato crops simply because growers are able to keep their plants dry. This is not possible with outdoor crops or those grown under plastic in southern Europe. Tomato growers were among the first to develop Integrated Crop Management (ICM) production protocols with their customers. These became the NFU/Retailer ICM protocols, now the Assured Produce Protocols. Glasshouse tomato growers currently represent a higher level of registration and compliance with the Assured Produce scheme than those of any other crop. A little red tractor on food packs means they have been produced according to this scheme. Few, if any, pesticides are used on British tomato crops and the TGA objective is to eliminate all such use within 10 years. Some growers have already achieved this. No organophosphate or organochlorine pesticides are used on British crops and no herbicides. British tomato growers have eliminated the use of peat for growing their crops, most now being grown in rockwool, a clean, light material which provides ideal growing conditions and better crops. Other materials, such as wood bark and fibre and coco fibre (coir) are also being tested. The use of fossil fuels for soil sterilisation by steam has been eliminated by these systems, as has the use of chemicals such as methyl bromide for this purpose. Methyl bromide has been specifically targeted in environmental terms because of its ozone depleting characteristics. Organic crops are still grown in the soil.
Fertilisers and Water Nutrient and water recirculation systems, such as the nutrient film technique (NFT), were developed in the UK. NFT is used by a number of tomato growers and this eliminates all nutrient loss to the environment, except that from final plant decomposition. The plant roots are bathed in water and nutrients which then drain into tanks before being checked, adjusted and reused. Glasshouses now being built for tomato production have the facility for water and nutrient recirculation. Tomato growers are developing systems for composting of plant waste (removed leaves during the season and plants at the end of the season) to avoid the financial and environmental cost of this material going into land-fill sites. An increasing area of Organic crops is being produced.
Import Substitution About three quarters of current UK tomato consumption is of imported fruit. Most is from southern Spain and the Canary Islands and increasingly from Morocco. These involve lengthy transport by road or sea. There are also imports from Holland, Belgium, France, Israel, Italy, Poland, Portugal and South Africa, to name but a few.
A competitive British tomato industry would therefore also achieve environmental benefits abroad, by substituting for the fruit produced there for export to the UK. We are talking global warming!
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Food safety and environmental protection are absolute priorities for British growers. They pioneered the use of natural means of pest control to avoid sprays. They also all use bumblebees for pollination.
