Energy Return on Investment of “living off the land”: natural production, human labor, and petroleum
Updated: Oct 22, 2018
Stephen M. Coghlan Jr.
University of Maine
Orono, ME, United States
As projected by Limits to Growth and other biophysical analyses, economic shocks from resource depletion, pollution, and debt overload threaten our current standard of living. The prospect of ecological overshoot and impending economic decline has motivated some people to find alternate means to produce economic surplus, increase their self-sufficiency, withstand climate disruption, and disentangle themselves as much as possible from fossil-fuel-based monetary and financial systems. Generating wealth directly from nature via homesteading and other types of “living off the land” may hold promise, but energetic profitability and thus viability is largely unknown and likely varies tremendously among regions, technological implements, subsidies required from the main economy, and skills possessed by homesteaders.
We constructed energy-flow systems diagrams to model energetic costs and benefits of three activities typical of a representative Maine (USA) homestead: sustenance ice fishing, lightly-mechanized firewood harvesting, and artisanal maple syrup production. The fishing model is calibrated with empirical data on angler effort, harvest rate, and purchased inputs, along with assumed trophic relations in a lake food web. One scenario simulates unregulated harvest of warmwater fish in a nearby eutrophic lake, and another simulates regulated harvest of coldwater fish in a remote oligotrophic lake. Fish biomass provides 20% annual protein intake for 2 adults. The firewood model is calibrated with empirical data on human metabolic work, firewood yield, and purchased inputs, along with assumed rates of forest production and mechanical chainsaw work. Firewood meets 100% of home heating needs. The maple sugaring model is calibrated with empirical data on human metabolic work, sap flow, firewood combustion, purchased inputs, and syrup yield, along with assumed rates of forest production. Annual syrup production meets household demand (2 gallons) and surplus can serve as a value-added commodity (8 gallons) as currency for barter with other homesteads. Analyses are underway and results are forthcoming. Estimates of EROI will indicate profitability of activities in meeting sustenance needs and generating surplus for exchange, and estimates of Emergy Yield Ratios will provide non-market valuation of human labor and ecological work more appropriate during times of economic contraction. Further model refinement will include feedbacks from climate change that affect natural production and economic feedbacks from depleting fossil fuels that increase costs of purchased inputs.