Counting straw : the capacity of New Zealand's grain growing sector to supply straw for construction

Abstract

The New Zealand Government has made a commitment to build 100,000 new dwellings over the next 10 years under its Kiwibuild programme. It has also made a commitment, under the Paris Accord, to reduce greenhouse gas (GHG) emissions to 30 percent below 2005 levels by 2030. The embodied CO2 emissions of the materials used to build 100,000 houses are therefore a critical consideration. Increased use of bio-based materials, like straw, could significantly reduce CO2 emissions from the construction industry, but are New Zealand farmers able to produce enough straw? Floor plans of two typical timber framed three-bedroom Kiwibuild houses were adjusted to incorporate an experimental timber and straw bale wall panel system and the number of straw bales required was established. The quantity of straw produced annually in Aotearoa New Zealand and the number of bales available for construction was calculated using industry data. The results show that at current production levels there is enough straw available to build more than ten percent of the total number of detached houses consented in 2017, clearly demonstrating that the grain growing sector does have the capacity to supply enough straw.