MANURE AS A RESOURCE — ECOLOGICAL AND ECONOMIC CONSIDERATIONS IN BALANCE

Abstract

Nutrients in manure constitute an ecological and economic liability if managed as a waste for disposal.However, nutrients are the source of economic benefit when managed as a resource. By combining economic andecological analyses, the ecological benefits of nutrients in manure are conserved, their economic value is captured, andboth ecological and economic goals can be met. We derived a simple model to define the conditions required for manureto be recycled effectively and transported economically. The basic premise of the model is that ecological and economicconsiderations must be in balance at steady state for manure nutrient management to be sustainable. The model combinesthe cost of processing and transportation, the value of the crop yield response to the manure product and the steady statecapacity of the land to recycle macronutrients. The model predicts that processing, to increase macronutrient content orto decrease unit transportation cost, and use of manure products on high value crops could permit break-even distributiondistances for some manure products of more than 300 km. We then used estimates of manure and crop production inAlberta to calculate municipal N and P balances to determine the distance of distribution required to use manureeffectively (municipality as used here is analogous to county in many parts of the world). In 1991, municipalities withmanure nutrients in excess of that harvested as grain were adjacent to municipalities with nutrient deficits. We concludethat (1) equating ecological and economic aspects of manure distribution is feasible and may enhance the profitability ofagriculture, and (2) improved effectiveness in the use of manure resources may be achieved by nutrient conservation andharvesting, processing to increase nutrient retention and reduce transport costs, and application technologies to increasecrop response to nutrients in manure products.