Pair of NECAR fuel cell A-Class Mercedes
In the depth of the Great Depression, a family garden was essential as this Detroit family demonstrates. If oil grows scarce, hand-tended gardens may become the norm again.

The Real Cost of Food - A White Paper

An analysis of the environmental impact of food production

By Robert Vale & Michael Pritchard

How Do We Live?

Much of the focus on energy in terms of people's living has concentrated on the house and its embodied energy, the house as an energy consumer in the course of its operation, and the energy associated with transporting the occupants of the house. (see, for example, DETR, 1998) An important aspect missing from this list is the energy involved in running the people who live in the houses. From the perspective of sustainable energy, this aspect has received little attention. On examination it may turn out to be a very significant part of the energy equation if society is to move to a more sustainable future. The operation of the house has in the past been analysed to identify areas where improvements in life-cycle energy performance may be made, with benefits to both energy costs as well as to environmental sustainability. (Fay, Vale and Vale, 2000) The support of the occupants has similar energy and environmental dimensions.

Food and drinks have their own energy component. In the United States, for example, there are a variety of calculations relating to the transport of foodstuffs. Hahn (1997) quotes a study by Wilkins at Cornell University which shows that the average distance for food items to be transported from farm to table is 1300 miles. Hendrickson gives a figure of 1800 miles. There are of course many other energy components of other parts of the food production and food processing cycles. Life cycle analysis of food presents a vast area where improvements can be made. Some of these improvements apply very much to one of the more fundamental aspects of sustainability: Œthink globally act locally'. Like a lot of things to do with more sustainable futures the analysis of these improvements will challenge both attitudes and the way most people currently do things.

The National Impact of Personal Food Consumption

The intention in this paper is to concentrate on aspects that affect the household, with particular focus on support for the operation of the people, rather than the house or personal transport. But, to return first to food. According to the United Nations Food and Agriculture Organisation (FAO) an average adult male should consume food with an energy content of 3,200 kilocalories or 13.4 MJ per day, while an average female should have 2,300 kcal or 9.63 MJ.(Fisher and Bender, 1975) In a year these figures come to 4.9 GJ and 3.5 GJ respectively, an average of about 4.2 GJ per year or 11.5 MJ per day. For comparison, a "typical four-person household spends $1,000 a year on electricity. " (EECA, 1999) This works out to roughly 10,000 kWh per year, or 36 GJ. Of this total, 47% is used for hot water. So the annual food consumption of a household of four adults would be approximately equivalent to the energy they use for hot water.

The New Zealand population is about 3.6 million. This suggests that total food energy consumption should be around 15 PJ. This figure can be compared with the annual total delivered energy consumption for the New Zealand economy of 430 PJ (Ministry for the Environment, 1997) (which does not include the calorific energy content of the food eaten by the NZ population). Because of over-eating, the actual food consumption of New Zealanders is 39% in excess of the FAO recommendations, (Ministry for the Environment, 1997) so the energy value of the food actually consumed is nearly 21 PJ. This is a considerable quantity of energy, equivalent to about 5% of the national energy consumption. This calculation makes no allowance for the fact that some of the population are children, who eat less than adults, but it also makes no allowance for the fact that teenagers should eat more than adults.

The Total Energy of Food

The average figure for food consumption per head of 4.2 GJ per year (about 1,170 kWh per year, the energy in about 120 litres of petrol) is the energy provided by the food to those who eat it. However, it takes energy to grow the food, to manufacture the tractors and operate them, to make the fertilisers and pesticides, to package the food, to transport it to the shops and to sell it. This is known as "embodied energy". Research in the United Kingdom in the 1970s showed that the embodied energy needed to make food available to the population was five times the energy in the food. (Leach, 1975) Recent figures from Australia suggest that the energy overhead of food is now closer to 10 to 1. (Calculated from data in Treloar and Fay, 1998)

The data from Treloar and Fay show an annual figure for the total embodied energy of food and drink in Australia of 42 GJ per person, which can be compared to the recommended average dietary energy requirement of 4.2 GJ per year). If the Australian rate of over-consumption of food is similar to that of New Zealand, 39% in excess of UN FAO recommendations, the individual consumption would be 5.8 GJ per year, and the embodied energy multiplier would be 7.2. On the basis of these Australian figures, the total energy embodied in the current New Zealand diet represents 150 to 210 PJ (actual consumption of 21 PJ multiplied by embodied energy factor of 7.2 to 10). The national primary energy consumption for New Zealand in 1996 was 665 PJ (Ministry for the Environment, 1997b). If between a quarter and a third of the energy used by the country each year goes to feeding ourselves, how far have we progressed from the hunter/gatherer stage? There is also the consideration that, because we overeat, 60 PJ of this total, or about 10% of the nation's total energy consumption is completely wasted, contributing to ill-health, obesity and all the other environmental ills of over-consumption.

One of the issues that has continued to develop with little attention to its impact on the environment has been the assumption that if demand can be met, it should be met. It is assumed that if the product is available and in demand then it should be provided as long as the financial costs of its provision, transport and handling can be met by the market. What is not realised is that most of these costs ignore the mitigation of any adverse environmental effects arising out of this policy.

Food and Cities: the New Urbanism

There are two ways to look at this problem of food and energy: the first is to concentrate the development of cities so that they leave highly productive land available for food production. This is one of the arguments of the "New Urbanists" and the advocates of "Smart Growth". Even where this has been done it has not had an appreciable effect on the energy equations in the food life cycle. If the analysis of Jane Jacobs (1969) is to be taken seriously, it is likely that this solution actually increases the non-renewable energy content of foods. This is because urban populations use market forces to drive down the cost of food. The replacement of human labour with non-renewable energy is a major feature of " modern" agricultural production. Temporary energy fixes (not priced at their true environmental cost) are used to satisfy the market demand with serious implications for long-term fertility and productivity of the soil.

Food from cities: the New Suburbia

The second way to look at the problem of food is to recognise that for a vast proportion of the world's population the urban fabric is still an important source of food, locally provided. It is this second aspect that will be explored here, with some suggestions as to possible changes. The suburban "city" that is largely representative of urban living in New Zealand was once highly productive. Table 1 below, taken from data in the New Zealand Census for 1956 and 1971 shows the percentage of home food production that was achieved in quite recent times.

Table 1: Percentage of households growing more than 25% of consumption area other vegetables other vegetables potatoes potatoes

 :1956 1971 1956 1971
New Zealand 40% 34% 31% 22%
Auckland 20% 15% 12% 6%
Christchurch 43% 39% 35% 26%
All urban 33% 27% 24% 16%

(note: figures rounded to nearest percentage)

It is clear that, as with a number of issues relating to development we are moving from what was a more sustainable to a less sustainable situation. Although figures are no longer available, in part because the census questions were considered no longer relevant, it is clear from the discussion above on food and energy that there are serious energy and resource consequences of the changes in home vegetable production. A " more sustainable" solution would be to move back to where we were in the 1950s.

It should also be recognised that housing preferences in Australasia continue to suggest that the suburban home is the preferred model for the greater proportion of the population. If preferences change and if denser urban forms become accepted there is even more reason to address the issue of localising as much activity as possible. The suburb can do a great deal to contribute to more sustainable solutions. The basis of food production is land, nutrients and water. In low density Auckland - "In 1996, 98 percent of the city's residents lived on the Auckland isthmus, with the population density being 22 people per hectare, with the exception of the Gulf Islands which is below 0.4 people per hectare." (www.akcity.govt.nz/, 2000) - most houses have the source of all three ingredients. The suburban house has enough land surrounding it; sufficient rain falls on a large enough roof to supply more than enough water for food production; the household produces enough wastes to supply the bulk of nutrients and minerals. Detailed considerations of water supply and nutrient provision for food production are set out below.

a) Water for Food Production

According to MetroWater (1999), the company that supplies water to Auckland, in Auckland the average household of water users comprises 3.7 people, and consumes 220 m3 of water per year (220,000 litres, or about 160 litres per person per day). The annual cost per household is $191.40 for the water (at 87 cents per m3), plus $63 for the systems charge, and $360 for the wastewater charge, a total of $614.40 per year. It is assumed by MetroWater, in order to calculate the waste water charge, that 75% of the water arriving at a house leaves it through the sewer. MetroWater do not know how much water is used for watering gardens, although they say that a hosepipe or sprinkler uses 1,800 litres per hour. Twort et al (1994) quote the following values for watering the garden; 25%-50% of total annual domestic demand in the USA, 33%-55% of total annual demand in South Australia, and 35% of total domestic demand in Melbourne (1982 data). These values average to 39.6%, but if the Melbourne value is assumed for Auckland, the annual water consumption for gardening would be 77,000 litres per household, costing the household $67 per year.

This water does not need to be purified to drinking standard ­ when it rains the garden gets watered with raw rainwater. It would be reasonable to collect the rainwater to water the garden when it does not rain. An average New Zealand house has a floor area of 150 m3 (Statistics New Zealand, 1995). It can therefore be assumed to have a roof area of at least 150 m3 since the majority of houses are single-storey. Auckland has a rainfall of around 1250 mm per year (IHVE, 1971) so the annual collection of water from the roof, allowing 20% losses for evaporation, would be 150,000 litres. This is more than enough to provide all the water needed for the garden.

Given that the water currently used for gardens represents 20% of Auckland's total consumption (domestic supply is 58% of the total, garden water is assumed at 35% of domestic) the use of roof water for gardening would offer an immediate water saving for the city. In fact the annual roof water supply would be adequate for both the garden and wc flushing, which typically uses another third of total domestic supply. Flushing is another example of a water use which does not require water of potable quality.

The use of water from roofs for garden watering and wc flushing would cut Auckland's total annual water demand by nearly 40%. The value of the saved water to each household would be $134 per year.

b) Nutrients for Food Production

In a number of surveys (Pritchard, 1992 and Hammonds, 1996) it is noted that a high proportion of domestic waste, at least 50% by mass, at present finding its way to landfill, is " organic" and compostable. In energy terms alone this is a significant issue. In terms of recoverable resources it will become an increasingly important issue. The best place to deal with this issue is at source, rather than trying to separate the compostable waste from the other waste after collection. The householder can use the waste as a resource to make compost for the garden, closing the loop by returning the nutrients in the waste to the soil. The result would be that 50% of household waste would no longer become "waste", it would become something of value. Waste from non-gardening households, restaurants and parks could be collected and composted in local centres, then returned to gardeners.

Leach (1976) provides data that demonstrate that for vegetables, the embodied energy attributable to fertilisers may vary from 11% of the total embodied energy for fresh peas, to 52% for potatoes and 57% for Brussels sprouts. By using domestic organic waste to produce compost to replace fertilisers, home gardeners could eliminate their need for oil-based, and arguably unsustainable, fertilisers. In addition, home production of vegetables would almost eliminate their embodied energy.

The Effect of Local Production on the Transport of Food

The transport of food uses a considerable amount of energy. Road transport uses 4.5 MJ per tonne per km (Baird, 1994) The average food item in the USA is said to travel between 1300 and 1800 miles (approx 2100 to 2900 km). Given that Auckland is about 1800 km from Sydney, and other parts of Australia are more distant, it seems reasonable to assume that food in New Zealand travels on average a similar distance. (The following calculations are based on the assumption that the food/transport equation for New Zealand is similar to that of the United States. A travel distance of 2400 km is used. Some of New Zealand's food travels less than 2400 km, but many of the imported foods travel a far greater distance. This is an area in which further research is needed).

According to data provided by the Heart Foundation (1993) a person should be eating roughly 1.3 kg of food per day. Allowing for children who might eat less, this could be assumed as 1 kg per person per day for the whole population. If a person eats 1 kg of food per day, the energy used just to transport it will be 10.8 MJ per day. (4.5 MJ per tonne per km x 2400 km /1000 kg per tonne) This is also more-or-less the amount of energy that the food provides as energy to the person who eats it. Just the transport of our food takes as much energy (from oil) as the food gives us; in a very real sense we are eating oil. This is the cost of global trade. In a year, each person's food will require 1,100 kwh in transport energy alone.

The population of New Zealand is 3.6 million, so each day the country is using 39,000 GJ for transporting food, or 14.2 PJ per year. This transport energy is provided by petroleum products, and results in an annual CO2 emission of just over a million tonnes, or 300 kg for each person (based on the figure of 0.27 kg CO2 per kWh of petroleum products. DETR, 1996) This may not sound like a lot, but taking the average household size of 3.7 people which is assumed by MetroWater, (MetroWater, 1999) each household in the Auckland area is responsible for the emission of over a tonne of CO2 each year, just for transporting its food. A tonne is the weight of a car - if each Auckland household tipped a car into the sea each year there would be an outcry, but a tonne of invisible carbon dioxide "tipped" into the atmosphere goes un-noticed, although its long-term effects on the environment may be as bad as tipping cars into the sea.

If, say, 50% of food were produced reasonably locally, with a travel distance of 100 km from producer to consumer, the emissions for transporting food to each household would be only 90 kg per year, which is a reduction of about 90% compared to the current situation. This would not only have environmental benefits, it would provide increased local employment. More importantly, if some of this production were " on site" it would have significant total impact.

The Impact of a Modest Increase in Home Food Production

What would be the effects of home production of foods? The Heart Foundation's "Food Pyramid" (National Heart Foundation of New Zealand, 1993) recommends that we eat 14 servings of food per day, of which 5 should be fruit and vegetables. If a household were self-sufficient in fruit and vegetables, it would be producing just over 35% of its total diet on this basis. It was shown above that New Zealand's current energy expenditure on food may be as high as 210 PJ. If every household grew all their fruit and vegetables, the saving would be 73.5 PJ per year, a reduction of about a third. If a quarter of New Zealand households were to grow a quarter of their needs for fruit and vegetables, it would reduce national energy consumption by 4.6 PJ. This is not at all an unreasonable target; this level of performance has been exceeded in the past according to the census data quoted earlier. Averaged over all the households in New Zealand this is the same as saving about 1,300 kWh per household per year. This would be a national saving in direct money terms of $126 million.

The Benefits of Home Production

The conclusion is that we should return to some of our more sustainable ways. As suggested in the title, 20 minutes a day gardening, capturing excess water and conserving nutrients by recycling "waste", might make for a more sustainable country. By providing exercise and fresh food this activity might help us to stay healthy; by saving money it might help us to become wealthy; in terms of sustainability, it might very well be wise.


DETR (1998) Building a Sustainable Future: Homes for an Autonomous Community General Information Report 53, Department of the Environment, Transport and the Regions/BRECSU, Garston, Watford

Fay R., Vale R. and Vale B. (2000) "Assessing the Importance of Design Decisions on Life Cycle Energy and Environmental Impact" PLEA International Conference, 2 - 5 July, Cambridge

Hahn N. (1997) "Growing a Healthy Food System" Journal of the American Dietetic Association Sep. Vol. 97 No. 9, p. 949 (2)

Hendrickson M. (1997) The Kansas City Food Circle: Challenging the Global Food System PhD Thesis, University of Missouri - Columbia

EECA (1999) Energy Wise Home Issue 2 December, p. 2

Fisher P. and Bender A. (1975) The Value of Food Oxford University Press p 22

Ministry for the Environment (1997) The State of New Zealand's Environment Ministry for the Environment, Wellington. p 3.17 and Table 3.2 pp 3.5-3.7

Leach G. (1975) Energy and Food Production IIED, London p 8

Treloar, G. & Fay, R. (1998). The Embodied Energy of Living, RAIA Environment Design Guide, The Royal Australian Institute of Architects, August, GEN20, pp.1-8

Ministry for the Environment (1997) The State of New Zealand's Environment Ministry for the Environment, Wellington. p 3. 21

Jacobs J. (1969) The Economy of Cities Random House, New York

http://akcity.govt.nz/about/intro/index2.htm accessed on 17 Feb 2000

MetroWater (1999) personal communication Renee Shirley 22 June 1999

Twort A., Law F., Crowley F., Ratnayaka D. (1994) Water Supply Fourth Edition Arnold, London. p 9

Statistics New Zealand (1995) Facts New Zealand Statistics New Zealand, Wellington. p 96

IHVE (1971) IHVE Guide Book A 1970 Institution of Heating and Ventilating Engineers, London. p A2-24

Pritchard M. (1992) North Shore Recycling Survey: Sample Survey of 300 Households December 1990 - May 1991 Auckland

Hammonds B. (1996) Domestic Waste Reduction: Promotion of Strategies at the Household Level MSc Thesis, University of Auckland

Calculated from data given in Leach G. (1976) Energy and Food Production IPC Science and Technology Press, Guildford, pp. 104-106 and 113-116

Baird G. (1994) "The energy requirements and environmental impacts of building materials" in Dawson A. (ed) Architectural Science: Its Influence on the Built Environment Proceedings of the 28th Conference of the Australian and New Zealand Architectural Science Association, 26-28 September Deakin University, Geelong, Victoria, Australia p 10

National Heart Foundation of New Zealand (1993) Number Crunching (pamphlet) The National Heart Foundation of New Zealand, Auckland

DETR (1996) Non-Domestic Building Energy Fact File Department of the Environment, Transport and the Regions, London

MetroWater (1999) loc. cit.

National Heart Foundation of New Zealand loc. cit.

Robert Vale and Michael Pritchard are faculty members at the Sustainable Design Research Centre, University of Auckland, New Zealand

Times Article Viewed: 4885
Published: 08-Jun-2001


blog comments powered by Disqus