3. Households and GHG emissions

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Australian households generate a lot of greenhouse gases – mainly from transport, heating and cooling, appliances and wastes (in landfill). Most families, however, can lower their greenhouse gas emissions and save money by reducing their energy bills. We can also save money and energy choosing carefully what we buy, for example, heavily packaged products require more energy to manufacture and transport. Buying secondhand is very popular, makes good financial sense and gives products a second life. A useful guide is the four Rs – refuse, reduce, re-use and recycle.

You are able to use the Australian Greenhouse Calculator to see what savings could be made by your family if such changes were made. Try it!

Australian households generate at least one-fifth of Australia's greenhouse gases – more that 18 tonnes per household each year. Averages provide only part of the picture because households can vary greatly in the amount of greenhouse gas emissions. Depending on where you live and your lifestyle, annual greenhouse gas emissions can vary from as low as 3 tonnes up to 30 tonnes or more.

An average Australian family's greenhouse gas emissions

An average Australian family's greenhouse gas emissions

Source: Adapted from Global Warming Cool it!, copyright Commonwealth of Australia, reproduced by permission, www.portstephens.nsw.gov.au/files/217567/File/Globwarm_Cool_It.pdf

Ecological footprint

Ecological footprint measures our impact on the Earth. It is a complex but useful tool that allows us to work out our impact as an individual, family, community, country or world. For example it tells us that as a global community we are consuming more resources than the Earth can sustainably provide. Currently we need about 1.5 Earths to meet our average resource needs. (Access the Living Planet Report, 2010 at http://wwf.panda.org.)

We all have ecological footprints. It's the size that differs. How big is your ecological footprint?

You can measure your personal, family and school footprint using the calculators provided by EPA (Victoria) at: www.epa.vic.gov.au/ecologicalfootprint/calculators/default.asp

The ecological footprint measures how much nature we have, how much we use, and who uses it. It shows us how much biologically productive land and water a population (an individual, an organisation, a city, a country, or all of humanity) requires to support current levels of consumption and waste production, using prevailing technology.


The most significant factor contributing to the Australian Ecological Footprint is carbon dioxide emissions from fossil fuels (constituting approximately half of the total Australian Ecological Footprint).

The animation, Carbon footprint provides you with more information.

Embodied energy

It takes a lot of energy to build a house. The most obvious energy comes when the builder, the carpenter, and the other tradespeople construct it. However, there is also a great deal of 'hidden' energy that was used to make and transport the building materials to the site. The energy that is consumed by these processes is called 'embodied energy'.

Take, for example, clay bricks. It takes energy to extract the clay, to transport it to the brickworks, to mould the bricks, to fire them in the kiln, to transport them to the building site and to put the bricks into place. It also takes energy to manufacture the equipment and materials needed to manufacture a brick. So you can see that there is a lot of energy, both direct and indirect, used to make clay bricks.

There is a great deal of embodied energy in the buildings and houses of Australia. One scientist has estimated that it is equal to ten years of Australia's total energy consumption!

Embodied energy is linked to carbon dioxide emissions. On average, 0.098 tonnes of carbon dioxide are produced per gigajoule of embodied energy. This means that if we can reuse or recycle materials – whether it is aluminium cans, or building materials – we can 'save' on the amount of carbon dioxide produced.

For example, the reuse of building materials commonly saves about 95% of embodied energy. However the savings from recycling of materials for reprocessing varies considerably, with savings of up to 95% for aluminium but only 20% for glass.

How much embodied energy is there in a house? Materials such as concrete and timber have the lowest embodied energy intensities but are consumed in very large quantities; whereas the materials with high energy content such as stainless steel are used in much lesser amounts. Thus the greatest amount of embodied energy in a building is often in concrete and steel.

Embodied energy in a house by material group

Embodied energy in a house by material group

Source: © CSIRO Australia

Green power: switching to a cleaner environment

Burning coal to produce electricity is a major source of greenhouse gases. Green Power is a national program to promote electricity generated from clean, renewable energy sources.

When you buy a Green Power accredited product, your electricity retailer purchases energy from renewable sources such as solar, wind, biomass and hydroelectricity sources.

Accredited retailers must not only source electricity from existing renewable energy sources, but must also contribute to the development of new generators using these renewable sources.

For more details, contact your electricity retailer or call Sustainability Victoria on 03 8626 8700 or 1300 363 744.

Cars of the future

The car is central to our current way of life, but it is also a major source of greenhouse gases. Developing a car that is non-polluting has been a dream of many designers. Cars powered by electricity and hydrogen have been designed and tested.

A number of carmakers are developing what are called hybrid cars. The Toyota Prius, for example, is a hybrid car that uses a small petrol engine with an electric motor. It provides low fuel consumption and low emission levels. Unlike fully electric cars, the Prius does not rely on heavy banks of batteries and nor do the batteries it uses need to be recharged. Recharging is done while the petrol engine is in use. The whole process is controlled by computers.

Another car close to production is the aXcess Australia concept car. This car is being developed by the CSIRO's Australian Automotive Technology Centre in partnership with private companies. Engineers call this car a 'series hybrid'. The engine it uses drives a generator, which powers an electric motor that powers the wheels.

The major problem in a hybrid engine is the storing of electrical energy required for acceleration or increased-load situations, such as climbing a hill. The CSIRO has solved this problem by combining its own designs for a supercapacitor and a lightweight gel battery. Together these form what they are calling a 'surge power unit'.

A simpler approach being used in Australia is to run a purely electric car. It is now possible to convert small petrol cars to run on electricity by swapping the motor for an electric one and adding a bank of batteries. The car is charged up using a simple power point at home. New cars designed specifically to run on electricity are also being designed and tested. Of course, green (renewable) power should be used to run such cars so that greenhouse emissions are kept to a minimum. Indeed it may be the case that running electric cars using coal-generated electricity would produce more greenhouse gases than using a petrol engine!

Heating and greenhouse gas emissions

Heating houses, particularly in cold climates, can generate many tonnes of greenhouse gas each year. The amount depends on many factors including house size, the size and direction windows face, and the type of fuel used.

Most homes in Australia are heated by natural gas or electricity. Other sources such as LPG, oil, wood and kerosene are used in some areas.

A range of heating appliances has been developed to use the different energy sources. These are described below.

Natural gas, LPG and oil

There are two types of heaters that use gas, LPG or oil. Space heaters are located in a room, and heat that room and adjoining areas. Ducted heaters are often located outside the house or in a cupboard. They heat air or water, which is circulated around the house to heat most, or all of, the house. Natural-gas heaters carry energy labels that show their energy efficiency.


There are four major types of electric heater:

  • fan heaters and radiators are the most common. They are compact and portable, and are often used for occasional heating or as main heaters in mild climates where little heating is required.
  • convection heaters are electric heaters that operate by enclosing radiator bars in a vertical box, with natural airflow drawn in from below, so no fan is required.
  • off-peak electric heaters use electricity overnight to heat up heavy blocks of material in a heat bank or to heat up a concrete slab floor. The stored heat is then released during the day, heating the house.
  • reverse-cycle air conditioners can be used for heating, as well as cooling. Instead of removing hot air from inside and pumping it outside (as they do when cooling), when heating, they cool the air outside and deliver the heat they have extracted from the outside air to the indoors. Reverse-cycle air conditioners are up to three times as efficient as ordinary fan heaters. Reverse-cycle air conditioners carry energy labels which show their energy efficiency.

Wood can be used as fuel in an open fireplace, or in a slow combustion heater, which is usually a metal box with a metal or glass door. A slow combustion heater is typically at least five times as efficient as an open fire. Briquettes, coal and coke can be burned in many slow combustion heaters.

Kerosene heaters burn kerosene to produce heat within a room. They are usually portable heaters used to heat small areas.

More information on types of heaters is available from your state Energy Information Centre, or local electricity and gas suppliers.

Reducing greenhouse gases

Greenhouse gas generated by heating can be reduced by:

  • improving the energy efficiency of the building by insulating and draught-proofing
  • increasing north-facing windows
  • adding north glass: this collects energy from the winter sun
  • selecting more efficient heaters
  • using a lower greenhouse-impact fuel
  • heating for shorter periods or to a lower temperature
  • double-glazing windows (this reduces heat loss through windows by 40%)
  • in conjunction with insulation and solar design, using heavy materials such as a concrete 'slab-on-ground'.

Types of cooling

Australians use portable fans, ceiling fans, evaporative coolers and air conditioners to keep cool during the hot months of the year. All of these appliances are powered by electricity and thus contribute to greenhouse gas emissions.

Fans create a cooling effect by moving air over people's bodies. As the airspeed increases, moisture evaporates more rapidly from the skin, removing more heat.

Portable fans: These typically use little energy (their power rating is about 40 watts), and generate one kilogram of greenhouse gas every 25 hours of operation.

Ceiling fans: These are permanently mounted on the ceiling of a room. They are very effective, and quiet. Typically, these use a little more energy (their power rating is about 60 watts), and generate one kilogram of greenhouse gas every 15 hours of operation.

Evaporative coolers: These range from portable units mounted on wheels that cool one room, to large, roof-mounted units with ducting, which cool a whole house. Evaporative coolers are most effective in places where summers are hot and dry. They are essentially large fans that blow air through water-soaked panels of fibre. The evaporation of the water cools the air and humidifies it. Evaporative coolers generate about a kilogram of greenhouse gas every 12 hours per room cooled. That is, if an evaporative cooler is used for four rooms, it will generate about one kilogram of greenhouse gas every 3 hours.

Air conditioners: These work in the same way as a refrigerator. A compressor pumps a refrigerant fluid around through pipes. The refrigerant absorbs heat from the room, then pumps it outside. Air conditioners may be simple wall- or window-mounted boxes, split systems (which have a separate cooling module connected to the other components by thin pipes), or large central units with ducting to a number of rooms. Air conditioners use more energy and generate more greenhouse gas than other forms of cooling but can often provide superior comfort in extreme heat, especially in humid conditions. Typically, an air conditioner generates about 1.5 kilograms of greenhouse gas per hour when cooling a living room during the day. When cooling a bedroom at night, around 0.5 kilograms of greenhouse gas is generated each hour, as bedrooms are smaller, there is no hot sun, and outside air temperature is cooler. Some air conditioners can also be used for heating. These units, called 'reverse-cycle air conditioners' or 'heat pumps', are discussed in the section, Heating and greenhouse gas emissions.

Cooling and greenhouse gas emissions

Air conditioners can generate several tonnes of greenhouse gas each year in hot climates.

Greenhouse gas generated by cooling can be reduced by:

  • insulating and shading the house
  • using fans and evaporative cooling in preference to air conditioning
  • selecting an energy-efficient air conditioner
  • switching off cooling appliances when you are not using the room
  • ensuring doors and windows are closed and draughts sealed when using air conditioners
  • wearing light, comfortable clothes instead of switching on coolers.


Few homes in Australia are without some form of refrigeration to keep food longer and drinks cooler.

There are three basic refrigeration appliances: the single-door refrigerator, the two-door refrigerator and the freezer:

  • Single-door refrigerators have a single outer door. Inside the older units, there is often a freezer compartment with its own door or hinged cover. Some single-door refrigerators have no freezer compartment as they are designed to be used with a separate freezer.
  • Two-door refrigerators have two separate outer doors. One door provides access to the fresh food compartment, while the other provides access to a freezer compartment. Most two-door refrigerators have one door located above the other, but some large units (sometimes called refrigerator/freezers) have the two doors side-by-side.
  • Freezers are available in two different styles: chest freezers, which have lids that open on top; and upright freezers, which look like single-door refrigerators.

Most pre-1995 refrigerators and freezers used CFCs to form their foam insulation, and in their compressors. To minimise damage to the ozone layer and greenhouse emissions, it is important that the CFCs are removed from their compressors before they are disposed of. Your local environment authority can tell you where this can be done.

Refrigeration and greenhouse gas emissions

Refrigeration is one of the largest contributors to household greenhouse gas emissions. A large, inefficient refrigerator can generate around two tonnes of greenhouse gas each year. New refrigerators carry energy labels, which show their energy consumption under standard conditions.

Greenhouse gas generated by refrigeration can be reduced by:

  • ensuring good circulation around the coils at the back of the refrigerator. This can save up to 150 kilograms of emissions every year.
  • placing refrigerators and freezers in cool spots, out of the sun. This can save up to 100 kilograms of emissions every year.
  • putting cold items back in the refrigerator immediately after use. Don't put warm food or drink into the refrigerator.
  • ensuring door seals are clean and the door closes properly. This can save up to 50 kilograms of emissions each year.


Cooking generates greenhouse gases by using fossil fuels directly or indirectly (in the form of electricity) unless wood or hydroelectricity is used. A large household can generate up to two tonnes of greenhouse gas per year as a result of cooking.

The greenhouse gases generated by cooking depend on the fuel source used, the efficiency of the cooker and/or saucepan, the amount of cooking done and the way cooking appliances are used.

Many families cook with natural gas. Natural gas consists mainly of methane, which is the simplest hydrocarbon. Natural gas, when burnt, emits less carbon dioxide per unit of energy than any other fossil fuel. An all-electric household, for example, would produce five times the quantity of carbon dioxide emissions produced by a household using natural gas for hot water, cooking and heating.

Methane is a powerful greenhouse gas. One kilogram of methane traps as much heat as 21 kilograms of carbon dioxide. Therefore gas appliances must be installed correctly to ensure no natural gas leaks into the environment.

In addition, poorly controlled emissions from the combustion of natural gas can reduce indoor air quality and, under some conditions, may even be harmful to health. A flue (or chimney) should always be used when burning natural gas.

Natural gas usage in Australia is governed by rigorous industry technical standards and the industry has a good safety record. In the past ten years, the gas industry has established industry standards for gas appliances to ensure emissions are well below acceptable limits.

As well, appliance manufacturers have initiated research and development programs to develop improved burner technology, some of which have attracted export interest. Other initiatives include the laboratory testing and approval of all gas heaters for sale, free home environment testing, and low-cost heater servicing.

Greenhouse gas generated by cooking can be reduced by:

  • using efficient cooking methods. For example, putting lids on pots, simmering gently instead of vigorously, and using a pressure cooker. These methods can save up to half the emissions generated during cooking.
  • using a toaster rather than a griller to cook toast
  • reheating meals in the microwave
  • using a fan-forced oven. They are up to 35% more efficient than conventional ovens
  • thawing food before cooking it.

Hot water

A range of appliances are available to heat water for domestic use. The most important ones are described below:

  • small electric storage tank: These may be located under a kitchen bench, in a cupboard in the laundry, bathroom, hallway, or outside. They are typically cylindrical in shape, and less than 1 metre high and 0.5 metres in diameter. Water is heated by passing electricity through a heating element, similar to heating water in an electric kettle.
  • large electric storage tank: These are typically cylindrical in shape, taller than 1 metre and at least 0.5 metres in diameter. They are often connected to a separate meter and a cheaper 'off-peak' electricity tariff which only allows heating to occur overnight (with occasional daytime boosting, in some cases). Large quantities of hot water are stored to supply hot water needs throughout the day.
  • electric heat pump: This is a new type of very high efficiency hot-water service, which extracts heat from the surrounding environment – effectively solar energy. It has a large storage tank, but also an electric motor and compressor like that of a refrigerator, and large panels which may be covered with water droplets when operating in cool weather. It uses around a quarter of the electricity of a normal large electric unit.
  • natural gas or LPG: Two types of gas/LPG hot-water service are common. Storage hot-water services are relatively large cylinders or boxes about 1.5 metres tall, with a gas burner in the base. The burner switches on and off to keep the water stored in the tank hot. They are often located outside, or in a laundry.
  • instantaneous gas hot-water services are small boxes, usually mounted on a wall in the laundry or kitchen, or outside. These heat water only as it flows through them, and do not store any hot water. Gas hot-water services carry energy labels. Lists are available from the Australian Gas Association or your local gas supplier.
  • solar: All solar hot-water services have glass-covered panels to collect the sun's heat. In most parts of Australia, some boosting is required to top up the sun's heat in cold, cloudy weather. Electricity, gas, LPG or wood can be used for this.
  • wood, briquettes and coke: Some country households use solid fuel heaters or stoves to provide both hot water and home heating.

Hot water and greenhouse gas emissions

Hot water use can generate up to six tonnes of greenhouse gas each year. This not only depends on how much hot water is used and its source of energy, but also on losses from the hot-water service. Losses may make up around half of total water-heating energy.

Greenhouse gas emissions from hot water can be reduced by:

  • reducing your water consumption
  • buying an energy-efficient water heater that uses solar energy, electric heat pump or natural gas. Gas water heaters carry energy labels to help you choose efficient models.
  • reducing the losses from an existing hot-water service, pipes and fittings by wrapping them with extra insulation
  • fixing dripping hot taps.
  • fitting a water-efficient showerhead or flow-control device
  • using cold water or less hot water for dishwashing and clothes washing
  • using an energy-efficient dishwasher on economy cycle
  • using a water-efficient washing machine (frontloaders are usually better than toploaders)
  • making sure that washing machines are fully loaded. Washing a full load or only a few socks generates almost the same amount of greenhouse gas.


Waste is any material that is left over after being used, that no longer is needed for its original purpose. Most kinds of packaging are only used once before they become waste. Other products like clothes and shoes may be used for years before they are no longer needed. Other items like electrical goods can become waste when they are broken. When preparing fresh food, parts of the fruit, vegetables or meat will not be used.

When something becomes waste, we need to choose what we will do with it:

  • Some waste can be reused for another purpose, eg reusing a jar as a vase
  • Many items of waste can be recycled, eg aluminium cans may be reprocessed to make new cans
  • Green waste can be composted or used as mulch, eg fruit and vegetable scraps can go into a compost bin
  • We can avoid some waste by repairing broken products
  • Many items cannot be recycled, reused, composted or repaired. A lot of these materials need to go into the rubbish where it will be sent to a landfill site, eg meat products.
  • A few items of waste have toxic substances and require special disposal, eg unwanted house paint
  • When waste is disposed of into the environment it becomes litter or pollution.

Often waste can be avoided by only purchasing what we need. A large percentage of food is dispose of because it was not eaten in time.

Landfill sites can generate large amounts of methane gas. The warming properties of 1 kg of methane gas are equivalent to 21 kg of carbon dioxide. Some old, unused landfill sites are designed to harvest this methane and generate electricity.

When we create compost and mulch from green waste we are storing carbon in the ground and avoiding additional methane and carbon dioxide.

We can all help to manage our waste. Managing our waste properly has a very positive impact.

Recycling, composting and waste disposal

What positive things can you do to help reduce greenhouse gas emissions?

A common rule now used by many people is the 4Rs: refuse, reduce, reuse and recycle.

When shopping, refuse excess packaging and paper. This could mean taking a basket to the fruit shop and not using plastic bags to carry individual items. Some bread shops encourage shoppers to purchase a cloth bag to carry the bread. This bag is reused and replaces plastic carry bags. Some supermarkets encourage their customers to reuse plastic bags.

You can reduce the amount of materials you use by buying in bulk, avoiding single-use disposable products and repairing appliances instead of replacing them.

There are plenty of opportunities to reuse materials. People who lived through the Depression years of the 1920s were very good at reusing materials such as building materials, string, rubber bands, paper bags and newspapers. We can learn from them by reusing containers, building materials and clothing.

If you no longer need things, don't throw them out, but see if others might use them. You might be able to sell them at a Sunday market or secondhand store. Many charities are keen to have secondhand goods and clothing to help families in need.

If you are unable to refuse, reduce or reuse, then perhaps you can recycle? Most local councils now have efficient recycling programs. Does your family remove paper and other recyclables from the household rubbish? Do you have a compost bin? Doing both these things will greatly reduce the amount of garbage you are sending to the tip.

How are greenhouse gases generated from household materials?

Containers generate greenhouse gases through the fossil fuel energy used in their manufacture. Recycling saves the energy needed to mine and process new materials, although processing of recycled material still requires some energy. The greenhouse factors used are described in the School Greenhouse Saver booklet (EPA Victoria).

Paper generates greenhouse gases not only through the fossil fuel energy used during its manufacture, but also through its decay in landfills, where it breaks down to form carbon dioxide and the very active greenhouse gas, methane. Reducing the use of paper also reduces the number of trees needed to make paper which results in a double benefit: an environmental benefit and also reducing carbon. Recycling not only saves some manufacturing energy (and trees), but also reduces the greenhouse gas emissions from landfills.

Food and garden waste generates greenhouse gases as it decays in landfills. Composting it (in a well-managed compost heap or bin) reduces its greenhouse impact by a factor of 3 to 4. This is because there is less of the very active greenhouse gas, methane, which is generated when it breaks down in the presence of air in the compost bin.

According to Australia's National Greenhouse Gas Inventory, decay of organic wastes in landfills generates 29 million tonnes of greenhouse gas each year. Around 30% of this is household food and garden waste – equivalent to around 1.5 tonnes of greenhouse gas per household each year. If these wastes were composted, they would generate only a quarter as much greenhouse gas as putting them in landfill.

Home renovation can produce a lot of waste – and greenhouse gas. One large builder's skip holds as much as 60 full, 120 litre wheelie bins. How much of this material could be recycled?

Clothes dryer/Clothes drying

Most Australians dry most of their clothes on a clothes line allowing clothes to dry using the sun and wind. But increasing numbers use an electric clothes dryer, particularly in winter. Using an electric clothes dryer generates around two kilograms of greenhouse gas per hour if the electricity is generated by burning fossil fuels. Drying a typical load of clothes in an electric clothes dryer takes 1.5 to 2 hours, generating 3 to 4 kilograms of greenhouse gas.

Clothes dryers carry energy labels, and lists of ratings are available from local electricity suppliers, some whitegoods stores, and State Energy Information Centres.

Greenhouse gas emissions from clothes drying can be reduced by:

  • washing clothes only when heavily soiled. Reducing the frequency of washing clothes will reduce energy needed for clothes washing and drying
  • drying clothes on a clothes line or rack, or above heating outlets
  • extra spin-drying or airing clothes to remove as much water as possible before drying. This can save up to two kilograms by reducing drying time.
  • running the dryer on a medium setting instead of high. This saves 10% on gas emissions.
  • Using a gas-fired clothes dryer instead of an electric one: this generates around a third of the greenhouse gas emissions of electric drying.


The current world food shortage has caught many experts by surprise. It was thought that more carbon dioxide in the air would help the growth of food crops.

This is not necessarily the case. In the future, changed rainfall patterns could put many crops at risk. Droughts, storms, floods and cyclones may destroy crops. As well, farmers are moving away from growing food crops toward producing the more profitable biofuels and livestock feed. Fishing stocks may be affected by climate change. As food prices rise, the world's poor will suffer.

Extreme weather events will have the most obvious impact on food production. More severe cyclones, storms and floods will wipe out crops. As well, higher temperatures lead to higher rates of water evaporation. In places like Australia, longer droughts will reduce the yields of many cereal crops like wheat and there will be less available irrigation water. We can already see these effects. Under such conditions, it will be difficult for many countries to maintain their production of food.

If droughts and other extreme weather events become more common, it will have a big impact on the availability of food. In the poorer regions of the world this could quickly result in millions of refugees seeking new homes. It raises questions such as: What will be done? Will they be given aid or will they be moved to regions that have more predictable weather?

Some agricultural experts claim the most sustainable way to produce enough food for the world is to reduce the size of farms and manage them using better ecological methods, such as moving away from mono-cropping.

Over half the world depends on fish as a major source of protein. Any impact of the fish stocks in the sea will quickly affect people.

Not all the food produced is used for people. Large volumes of grain are used to feed animals such as chickens and cattle. The more meat people want to eat, the more grain will be used to feed animals.

Biofuels sounds like a good idea. Plants are grown and then fermented to produce alcohol. The alcohol is mixed with petrol so that less petrol is needed. However, when corn or other food is used, there is less food for people and it adds pressure on food prices. There may also be pressure to clear more rainforest to grow them. Biofuels made from plants like grass could be a better alternative, although it requires a lot of energy to be produced. Algae biofuels are the most sustainable option available, but the technology at a commercial scale is not yet proven.

Genetic modification technology may be part of the solution to ensuring sufficient food is available for all. Crop varieties can be developed using this technology that are drought- and heat-resistant and produce higher yields. Varieties of crops may also be developed that have a higher resistance to particular insects or disease. There are many claims and counterclaims about the future benefits of genetic modification technology. This no doubt will be a discussion point in future years.

What can we do about the problem of food? You can start by making sure food isn't wasted. Also, buy food that is local and seasonal to reduce energy used for transportation. Try to grow your own food – herbs, small fruit trees and many vegetables are easy to grow, even in pots, wherever you have sunlight, soil and water.

Food choices

The food you choose to buy and eat will have a direct impact on the amount of greenhouse gases produced by your lifestyle. The major food groups and the associated greenhouse gas emissions are outlined below:

  • Beef and lamb: Cattle and sheep have a fermentation digestive system to digest grass and hay. The microbes responsible for the fermentation also produce very large volumes of methane gas. The warming properties of 1 kg of methane gas are equivalent to 21 kg of carbon dioxide. Cattle and sheep produce so much methane that all other greenhouse emissions due to this meat production are small in comparison. Any changes to cattle and sheep diet that reduces methane production will have a significant climate change impact.
  • Pork and chicken: Pork's major climate change impact is the production of cereal to feed the pigs which includes fertiliser plus the production of methane from the treatment of pig droppings and urine. This effluent could be used to capture methane and generate electricity. Of these meats, chicken has the lowest climate-change impact. Most of the impact is from producing the food to feed the chickens.
  • Fish and other seafood: The climate change impact depends on how much effort is required to capture the animals. Lobsters have the highest impact. Flounder, sole, bass and sharks all require a lot of effort, and therefore boat fuel, to catch. Of all the seafood, mussels have the least climate-change impact.
  • Dairy: As with beef, the greatest climate change impact is the cows' production of methane gas as micro-organisms ferment the food in the cows' stomach. The warming properties of 1 kg of methane gas are equivalent to 21 kg of CO2. Further greenhouse gases are produced when growing cattle fodder and grain, using tractors and milking machines, pasteurising and refrigerating the milk, transport and packaging of the different milk products. Ice-cream products require freezing and cheeses, lengthy processing.
  • Bakery goods: The use of electricity and gas to bake bread, cakes and other products is one of the major climate-change impacts. However when small amounts of milk or beef products are included in these items, their climate change impacts greatly outweigh those due to energy use.
  • Fresh fruit: The climate change impact of growing and distributing fruit is much lower than meat, dairy and bakery products. Therefore the contribution of fertiliser, use of tractors and transport, water and other agricultural services are the main greenhouse impacts. Differences occur due to distances travelled when fruits are seasonally available or when they are transported a large distance.
  • Fresh vegetables: The climate change impact of growing and distributing vegetables is much lower than meat, dairy and bakery products. Therefore the contribution of fertiliser, use of tractors and transport, water and other agricultural services are the main greenhouse impacts. Differences occur due to distanced travelled when fruits are seasonally available or are transported large distances.
  • Other fruit and vegetables: Fruit and vegetables may be canned, bottled, frozen, dehydrated or dried. Additional impacts arise from packaging, processing or, for some products, refrigeration.
  • Flour and grains, pulses, nuts and eggs: These foods make up the greatest proportion of most people's diets. Because these food products require the least processing, they contribute the least impact.
  • Processed foods, confectionery, condiments, etc: There are a wide range of processed foods that contain a complex mix of ingredients. The major inputs are from growing of sugar, cereal and beef along with the use of electricity and gas during production.
  • Non-alcoholic beverages: Packaging is a significant part of the climate-change impact. Many of these products contain sugar. Some contain fruit. Coffee beans are roasted.
  • Take-away food and dining out: Additional climate change impacts arise when eating out. There is often greater waste and the addition of extra electricity, gas, and cleaning and maintenance of the property.