Don’t let figures befuddle you; you can live a low-carbon life



Recent articles on low carbon homes and life cycle measurement difficulties left carbon groupies concerned about the complexity involved in measuring our emissions.

Measuring emissions isn’t as hard as they make out

While never just a back of the envelope calculation, measuring emissions is now relatively straight forward. Integrating the national input-output tables (financial flows between all that sectors that generate GDP) with national physical and social accounts for water, landuse, greenhouse gases, employment and so on, gives intensity figures for each dollar spent. That is, we can see the kilograms of greenhouse emissions per dollar spent on air travel, restaurant meals, a motor car or a visit to the doctor.

Multiplying the financial breakdown of a building project by these physical intensities gives the full life-cycle emissions of the building and its contents. Repeating this for the spending patterns of the inhabitants quantifies their carbon lifestyle.

A comprehensive report for the Australian economy – Balancing Act – was published in 2005 under the guise of triple bottom line accounting. The structural path analysis tool used with this whole-economy accounting reveals all inputs into the production chain and thus allows the search for lower carbon alternatives.

The Eora project has recently gone live to a limited set of specialists. This is a fully integrated global model revealing the carbon intensity of millions of production chains, showing each economy in detail with full adjustments made for international trade flows. So the time of “knowing nothing” or “it being too hard” is nearly over.

How does it work for houses?

The late Graham Treloar and colleagues at Deakin University used this “environmentally extended input-output analysis” to explore the physical intensity of construction types and the lifestyles lived therein.

Their work used energy units (gigajoules or GJ) to separate out the one-off or embodied cost of house building, and the recurring yearly operational costs of keeping it going. These can easily be converted to tonnes of carbon. Brown coal electricity and gas still rule in Victoria where the study was based.

The full life cycle picture of a building’s 30-year life with its occupant’s comings and goings provide messages critical to today’s carbon policy angst. For the full family energy budget of 100% over 30 years, the house build was 8% and operational energy (gas and electricity) took 22%.

Then come the interesting bits: personal belongings (2%), consumables (34%), financial services (8%), motor cars (22%) and holidays (4%).

The house build in the Treloar study was 1441 GJ embodied energy. Recurring energy was 3099 GJ over 30 years, with heating using 1440 GJ, appliances 643 GJ, hot water and cooking 613 GJ and lighting 402 GJ.


The 7-10 star designs now available could easily halve each recurring energy cost with solar passive design, triple glazed windows, solar hot water and plantation wood pellets for heating.

Decarbonising the electricity supply by photvoltaics or purchasing green power can help us get closer to the zero-carbon ideal. Renewable electricity does cost carbon: around 30 grams per kilowatt hour for wind and 100 gm/kWh for photovoltaics. Compare these to Victorian brown coal electricity at 1300 gms/kWh and then suburb-wide implementation gives substantial progress.

Decarbonising the embodied energy of the house build is more difficult and requires industrial processes to radically revamp. But even in Australia you can source good recycled product or aluminium made with hydropower rather than subsidized brown and black coal electricity.

An efficient house is a nice start, but you need to buy less stuff

Ministers for Climate Change run a mile from dealing with the carbon involved in consumables.

Today we churn through more stuff than in 2000, when Treloar’s study was done, so the figure of 2% for long-lived belongings may be a bit low. But the general premise if you want to lower emissions is to buy well and keep it for a long time.

A commonly purchased laptop computer has CO₂ emissions of 270 kg embodied in its manufacture and another 120 kg for the rest of its life emissions. So if fashion fads rule your life (or if, like my daughter, you drop your iPhone frequently) it all adds up.

Consumables at 34% (food, drinks, books, clothes and so on) are a large part of the energy inventory and thus carbon costs. But spending is what keeps the economy going, bankers happy and treasurers pontificating.

Our work shows that the more we spend the more we emit across the whole life cycle. This is clearly mapped in the Australian Conservation Foundation’s Consumption Atlas.

This atlas shows those leafy suburbs with high house prices emit on average two to three times per capita more than their poorer cousins on the city boundaries. So here a tension emerges between the hard slog of house design (where construction and materials plus operational energy equals 30% of the full 30 year life cycle) and the equivalent loading that comes from buying consumables.

The economy relies on shopping churn to keep optimism, maintain full employment, keep economic growth trundling along and our landfills overflowing. So unpalatable though it might be, the zero-carbon house requires a low-spend lifestyle to reap a double carbon dividend. Perhaps those triple glazed windows and photovoltaic panels will leave homebuilders financially stretched enough to make shopping even more painful.

Why not walk to the shops?

Motor cars are energy guzzlers and represented 22% of the household’s total lifecycle energy in this study. Each car has a manufacturing embodied energy cost of around 130 GJ and uses at least 100 GJ of fuel yearly.

Hybrids or small light cars which reduce fuel use by 50-70% are no brainers (and you should keep them going for ten years if possible). Focused life cycle analyses show that hybrids outperform conventional petrol and diesel cars across all impact categories by 50-90%, except that a hybrid’s waste streams are higher due to end of life treatment of batteries. Again a fuller decarbonisation is impossible unless the production chains for liquid fuels or electricity are themselves fully decarbonised.

More recent research by Peter Newton and colleagues at Swinburne University focused on a house’s gadgets and their carbon impacts; that is, the yearly recurring carbon costs. “Walk up” medium density housing is better than apartment blocks and detached houses. It should have gas-boosted solar hot water (500 kg CO₂ per year), the basis set of appliances with a “best of breed” energy rating (3000 kg CO₂ per year), gas cooktop and oven and microwave (300 kg CO₂ per year), compact fluorescent or LED lighting (400 kg CO₂ per year) and gas heating (2000 kg CO₂ per year).

This six tonnes or so of operational emissions can be partially offset by 4000 watts or more of photovoltaic panels. But remember this is less than 30% of the household’s carbon loading, so the main job is yet to be embraced.

Five evidence-based steps to living lightly

So there are five take-home messages from using whole-economy principles for greenhouse accounting:

    li>Build the house properly to more than 7 star standards and trade off space and opulence for year-round comfort and low running costs.

  • Populate this house with the “best of breed” appliances and change behaviours of using and consuming. Focus on high quality goods that last forever and transcend fads.
  • Become a low-consumption and high-savings household, investing in safe buffers for your family’s future. Spend time together rather than buying stuff.
  • Consume mostly fresh non-processed foods grown within your state and region.
  • Live close to public transport, walk and cycle. Use the car sparingly, keep it for ten years and buy a hybrid if you have the cash.