Professor Brenda Vale and Dr Robert Vale of Victoria University are respected experts on sustainable buildings. In their new book ‘Time to Eat the Dog: The real guide to sustainable living’, they claim that feeding a large dog has a larger environmental footprint than driving an SUV 10,000 km, while a cat is environmentally equivalent to a VW.
The mistake the Vales make is in ignoring the difference between the sources of energy to ‘construct’ pets and cars. Pets grow and live on food derived from photosynthesis, so they are part of a carbon neutral cycle. Furthermore pets are fed on waste meat which would otherwise decay, liberating carbon dioxide and some methane which has about 25 times the global warming potential of carbon dioxide. Some pet food, either caught by the pets or obtained from hunters is meat from pests such as rabbits.
The energy to make a car, and fuel it, comes from fossil carbon. This adds to carbon emissions. A Toyota Prado has a mass of 2.9 tonne. As I don’t know masses of glass, plastic and rubber in the vehicle, I’ll make a generous simplification and assume the vehicle is merely 2 tonne of steel. Manufacture of that amount of steel would emit about 4.4 tonne of carbon dioxide. If the steel were to be manufactured sustainably using wood charcoal, between 7000 and 30,000 Ha of forest, depending upon the local wood growth rate, would have to be set aside to produce one Toyota every 100 years. Quite a bit more than the Vales’ 0.41 Ha! My figure omits fabrication energy costs and transport of ore and charcoal to Japan. Fuel consumption for 10,000 Km (1100 L of biodiesel) requires 0.008 Ha if the most efficient microalga is used. The Vales are architects with an obviously poor understanding of ecology. I am left with doubts about their publications on sustainable building.
Farming’s biological emission of carbon dioxide does not contribute to global warming as it is part of a natural cycle, which is magnified at both the photosynthesis and respiration points by human management. Embodied energy in vehicles and machinery and fossil fuel consumption are serious ecological problems in farming as in most other economic activities.
Atmospheric methane concentration has increased by a factor of 2.3 over the past 150 years despite drainage of swamps and decimation of feral mammals. Increased farm animal numbers is an obvious suspect contributor. If less or slower release nitrogenous fertilizer were applied, both methane and nitrous oxide emissions could be lowered dramatically. As New Zealand is less dependent upon energy intensive farming than America and Europe, our farmers could be competitive from an intelligent approach to greenhouse gas emissions.
- written by Allen Cookson, Oxford
This article was first published in the November issue of Canterbury Farming.