Manure as a resource - Ecological and economic considerations in balance

Nutrients in manure constitute an ecological and economic liability if mana ged as a waste for disposal. However nutrients are the source of economic b enefit when managed as a resource. By combining economic and ecological ana lyses, the ecological benefits of nutrients in manure are conserved, their economic value is captured, and both ecological and economic goals can be m et. We derived a simple model to define the conditions required for manure to be recycled effectively and transported economically The basic premise o f the model is that ecological and economic considerations must be in balan ce at steady state for manure nutrient management to be sustainable. The mo del combines the cost of processing and transportation, the value of the cr op yield response to the manure product and the steady state capacity of th e land to recycle macronutrients. The model predicts that processing, to in crease macronutrient content or to decrease unit transportation cost, and u se of manure products on high value crops could permit break-even distribut ion distances for same manure products of more than 300 km. We then used es timates of manure and crop production in Alberta to calculate municipal N a nd P balances to determine the distance of distribution required to use man ure effectively (municipality as used here is analogous to county in many p arts of the world). In 1991, municipalities with manure nutrients in excess of that harvested as grain were adjacent to municipalities with nutrient d eficits. We conclude that (1) equating ecological and economic aspects of m anure distribution is feasible and may enhance the profitability of agricul ture, and (2) improved effectiveness in the use of manure resources may be achieved by nutrient conservation and harvesting, processing to increase nu trient retention and reduce transport costs, and application technologies t o increase crop response to nutrients in manure products.