Computes the Energy Return on Investment, a key metric for assessing whether an agricultural system produces more energy than it consumes. EROI is mathematically identical to energy use efficiency (EUE) but is the preferred term in energy and sustainability science literature.
eroi(energy_out, energy_in, include_solar = FALSE, verbose = TRUE)Numeric vector. Total energy output from the agricultural system (MJ/ha), including grain, straw, and any co-products.
Numeric vector. Total energy input invested in the agricultural system (MJ/ha), including all direct (diesel, electricity) and indirect (fertilizer manufacture, machinery depreciation) energy inputs.
Logical. If TRUE, includes captured solar
energy in the output. Default FALSE (standard practice).
Logical. If TRUE, prints informational messages
and interpretation. Default TRUE.
Numeric vector. EROI values (dimensionless ratio). Interpreted as follows:
Highly energy-profitable system
Energy-positive but moderate return
Break-even: energy output equals input
Energy sink: system consumes more than it produces
$$EROI = \frac{E_{out}}{E_{in}}$$
EROI is the fundamental metric of net energy analysis. In agricultural contexts, EROI typically ranges from 2 to 15 for conventional cropping systems, with higher values for low-input or conservation agriculture systems.
Hall, C.A.S., Lambert, J.G. & Balogh, S.B. (2014). EROI of different fuels and the implications for society. Energy Policy, 64, 141-152. doi:10.1016/j.enpol.2013.05.049
Murphy, D.J. & Hall, C.A.S. (2010). Year in review - EROI or energy return on (energy) invested. Annals of the New York Academy of Sciences, 1185(1), 102-118. doi:10.1111/j.1749-6632.2009.05282.x
Murphy, D.J. et al. (2022). Energy return on investment of major energy carriers: Review and harmonization. Sustainability, 14(12), 7098. doi:10.3390/su14127098
# Conservation agriculture with low input
eroi(energy_out = 59800, energy_in = 8500)
#> EROI computed: 7.04 (highly profitable).
#> [1] 7.04
# Conventional tillage with high input
eroi(energy_out = 40800, energy_in = 12500)
#> EROI computed: 3.26 (energy-positive).
#> [1] 3.26
# Multiple treatments
eroi(energy_out = c(40800, 50500, 59800),
energy_in = c(12500, 9800, 8500))
#> EROI computed: 3.26, 5.15, 7.04 (energy-positive, highly profitable, highly profitable).
#> [1] 3.26 5.15 7.04