Machinery contributes around 54% of the cotton farm input costs. Research conducted by the National Centre for Engineering in Agriculture (NCEA ) into on farm energy efficiency has found that for cotton production: * There is significant variation in energy use between cotton enterprises and this is largely due to irrigation. * Energy usage was 3.7 to 15.2 GJ/ha at a cost of $80 to $310/ha. *275 to 1,404 kg CO2 equivalent/ha of greenhouse gas emissions are generated.