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Health And 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:

  • A substantial reduction in energy use for heating glasshouses.
  • The almost complete elimination of pesticide use.
  • Major reductions in the use of fertilisers and their loss into the environment.
  • Substitution for imports with their associated "food miles" and lower environmental production standards.

People in glasshouses
Almost all tomatoes in Britain are grown in glasshouses. They are produced in our natural season and harvested between March and November. The major components of glasshouses are glass and aluminium, both very durable materials. If properly maintained, glasshouses will last for 50 years or more.

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. What is this polythene made from, how long does it last and what happens to it after use?

The weather in the spring of 2003 has been wet and cold in southern Europe, like the winter of 2001/2002. Salad crops have been badly affected by this and tomato fruit quality has been poor. Many tomato crops have also been 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.

Energy Use
In the 10 years to 1995, British growers reduced annual energy use by 25-30%. With a similar national tomato production of 125,000 tonnes, this represented a reduction in total energy use equivalent to 45 million cubic metres of natural gas or 10 million gallons of oil. It also gave an annual reduction in carbon dioxide emissions from fuel of around 90,000 tonnes.

During this period the majority of the production area was converted to use natural gas for glasshouse heating, resulting in les 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. The total reduction in CO2 emissions was therefore much greater than 90,000 tonnes.

Combined Heat and Power (CHP)
Combined Heat and Power (CHP) is one of the most exciting technical opportunities for the UK tomato industry. It involves the siting of electricity generating stations on tomato nurseries. These systems are fuelled by natural gas and produce electricity which is then supplied to local homes, hospitals and businesses via the national grid. The heat which is generated is used to heat the glasshouses, rather than being wasted through the cooling towers needed at power stations. Electricity is generated at around 80% efficiency compared with the 30% in the conventional power stations which would otherwise produce this power.

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 (75 hectares) of the UK tomato production area is now equipped, or in the process of being equipped, with CHP facilities. This figure is expected to rise further. Not heating this area of glasshouses by conventional means will save each year a further 50 million cubic metres of gas and 100,000 tonnes CO2 emissions. This figure again does not include the amount of CO2 which is extracted from the cleaned CHP exhaust gases and supplied to the glasshouse to feed the tomato plants.

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
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 use bumblebees for pollination.

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. At least one grower has already achieved this. No organophosphate or organochlorine pesticides are used, and no herbicides.

Crops are typically grown in isolated ‘substrates’, such as rockwool, not in the soil. The use of fossil fuels for soil sterilisation by steam has been eliminated by these systems, as has the use of methyl bromide for this purpose. Methyl bromide has been specifically targeted in environmental terms because of its ozone depleting characteristics.

Fertilisers and Water
Grower-funded research has resulted in substantial reductions in nitrate applications to UK tomato crops (upto 50%) and even larger reductions in nitrate emissions to the environment, such as in water courses. Phosphate application rates have been reduced to a similar degree over the past 10 years.

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
Few, if any, British tomato growers are more than 100 km from a supermarket distribution centre or wholesale market.

About two thirds of current UK tomato consumption is of imported fruit. Most is from southern Spain and the Canary Islands. Both involve lengthy transport by road or sea. There are also imports from Holland, Belgium, France, Morocco, Israel, Italy, Portugal and South Africa, to name but a few.

A competitive British tomato industry is therefore also achieving environmental benefits abroad, by substituting for the fruit produced there for export to the UK.

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