Executive Summary
AgriLINK New Zealand was commissioned by a multi-stakeholder group comprising MAF, Vegfed and the Energy Efficiency Conservation Authority (EECA) to conduct a pilot survey and scoping report on energy use and carbon dioxide emissions for the heated greenhouse industry. The survey was not representative of the industry but rather captured a range of greenhouse types, fuel types and regional locations.
Statistics are available for the size of the greenhouse industry but these are not separated into heated or unheated, fuel type or greenhouse type. An assumption was made that all greenhouse vegetable production was heated, which covers 250 ha, 56 percent of which is in the Auckland region.
The average energy intensity of the surveyed group was 1,600 MJ/m2 with a range of between 700 and 2,600 MJ/m2. An estimate of the industries national energy input is between 2 and 4 PJ.
On a production basis the energy input for the tomato sector, which accounts for 64 percent of the vegetable industry by area, was 38 MJ/kg tomatoes with a range of between 16 to 51 MJ/kg tomatoes.
The energy intensity of double skin plastic greenhouses was approximately half that of single glaze glass. Double glazed glass is not used because of the capital expense and reduced light transmission. While twin skin plastic is more thermally efficient than glass, yields may be less due to lower light levels, particularly as the plastic ages. North Island production was approximately half the energy intensity of the South Island.
On an expenditure basis energy represented 20 percent of operating costs and ranged between 6 – 27 percent.
The average gross carbon dioxide emissions were 125 kgCO2/m2 and ranged between 35 and 235 kgCO2/m2. These carbon emissions, at a carbon tax rate of $25/tCO2, mean an average tax of $3.10/m2 with a range of $0.80 to $5.90/m2. These average survey figures are higher than the likely industry average because of a bias in the survey towards coal users.
On an industry scale the total carbon dioxide emissions ranged between 90 and 590 kt CO2 per year. The impact of a carbon tax on the industry would be to add $2.25 million in extra costs, calculated using the lower end of the CO2 emission range, and a carbon tax rate of $25/tCO2.
Gaps that were identified for further analysis included improved understanding of both the industry profile and the statistical significance of the indicators. Further analysis is needed into the key variables of greenhouse type, fuel type and location. Several case study energy audits are needed to determine what energy efficiency measures are available and what their likely payback periods would be.
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