This information is intended for use by energy providers or those companies with surplus energy available from industrial or production processes which might be suitable for linking with glasshouse crop production.
All commercially significant quantities of tomatoes produced in the UK are grown in glasshouses. The most typical crop cycle involves planting in December or early January with harvesting between March and November.
Production through the winter is possible with the provision of lighting to supplement solar radiation, which is not otherwise adequate to achieve economic yields and fruit quality at this time of year under UK conditions. About 10% of the UK crop area is grown this way.
The major components of glasshouses are glass and aluminium, both very durable materials. Polythene-clad greenhouses are not generally used for UK tomato production, although most southern European and North African imports are produced under plastic.
A constant energy supply for heating the glasshouse is necessary throughout the cropping period and a suitable carbon dioxide supply is required to replenish and supplement the glasshouse atmosphere to achieve optimum production.
Over the past 20 years, British growers have reduced annual energy use by more than half for each kilo of tomatoes of the same type produced.
During this period the majority of the production area was converted to use natural gas for glasshouse heating, resulting in less of the emissions which would come from burning oil or coal. Carbon dioxide can be extracted from the clean exhaust gases when burning gas, to enrich the glasshouse atmosphere with CO2. This gives significant production benefits as well as further reducing CO2 emissions.
CO2 uptake by British tomato crops is estimated to be 25,000 tonnes per year.
Typical annual energy use for glasshouse heating is 450 kWh/m2 glasshouse area. More detailed information on this and the seasonal pattern of use is available on request.
CHP systems have been used by UK growers for some years but their exploitation has proven more difficult than elsewhere, Holland in particular, because of the effects of political and economic influences on the relative price of fuel (normally natural gas) and the value of electricity produced.
These systems are also now being fuelled by methane ('biogas') produced by anaerobic digestion (AD) of vegetable waste, crop residues or crops grown specifically for this purpose.
Tomato crops can be heated by surplus energy from industrial processes, which would otherwise be wasted. This can provide a significant saving in capital costs in electricity generation facilities if considered at an early development stage, as well as providing an opportunity for the production of a valuable and nutritious food.
CO2 generated from these processes can also be used to supplement the glasshouse atmosphere, if the combustion gases are clean enough (free from contaminants such as Ethylene and Nitrous oxides) to allow this use without damaging plants.
If the intention is to develop a glasshouse production facility on an 'energy' site, a number of issues are critical to such a development.
The UK tomato industry now consists of relatively few but large production companies. This has come about because of the need for economies of scale and efficiency in production, but also to meet the requirements of the retail sector. Total UK tomato production is around 190ha of glasshouse facility and the total value of the British tomato crops is approximately £160m.To establish a standalone company on a greenfield site and to operate it economically would demand a minimum production scale of around 5 hectares of glasshouse area in order to supply the multiple retail market. There should be room for potential further development. The site would also need to accommodate office buildings, storage facilities, roads, reservoirs and car parks. Initial investment for such a project (excluding land) would be of the order of £7m.
The site should be as level as possible, not at an excessively high altitude or exposed, not prone to flooding, with good road access, mains water and electricity.
Critical factors to be considered are:
Expensive though energy may be, reducing its cost will not on its own be sufficient to make a project viable. Operating a tomato production and marketing company in the modern economic and competitive environment demands the highest levels of multi-disciplinary skills as a first requirement.
Further help and guidance may be obtained by contacting the British Tomato Growers' Association at www.britishtomatoes.co.uk by emailing email@example.com or by telephoning 01243 554859.
Did You Know?
British Tomato growers use an army of over 40 million beneficial predatory bugs called Macrolophus in summer to keep pests out of their crops, reducing the need for chemicals.