Effect of local conditions and machinery characteristics on the environmental impacts of primary soil tillage

The interest in environmental assessments about agricultural processes is high and asks for tools for accurate impact evaluations. The methodology commonly used in these studies is the Life Cycle Assessment (LCA), of which the inventory phase (Life Cycle Inventory – LCI) is the essential and most complex step to fulfil, for agricultural productions in particular. The reason is that taking into account local variables such as soil texture and mechanical operative solutions for the agro-mechanical operations is difficult. The aim of this study was to perform a case study to quantify the environmental impacts through LCA of alternative ploughing solutions and to quantify the differences that occur when an analysis is fulfilled with inventories completed with two different tools. First, when a database furnishes average data (Ecoinvent) and, secondly, when the inventory is completed with a tool that considers local variables. In particular, the used new tool is ENVIAM (ENVironmental Inventory of Agricultural Machinery operations), which was developed to take into account local variables. Finally, a subsequent goal was to quantify the environmental impacts through LCA of alternative ploughing solutions. Using ENVIAM, mouldboard ploughs were compared with slatted ploughs and variables such as the number of ploughshares, the field shape ratio (i.e. the ratio of field length and width considering regular quadrangles) and soil texture differed. Fuel consumption and exhaust gases emissions were calculated as function of working time, engine load and European Standard Emissive Stage. The functional unit was “1 ha tilled in a primary soil tillage operation appropriately and completely carried out” and the International Reference Life Cycle Data System (ILCD) characterization method was used for the impact assessment. The most common implement present in Northern Italy, the 3 ploughshares mouldboard plough, was considered as baseline scenario. When working on medium texture soils, discrepancies with Ecoinvent were not negligible (less than 9% for Climate Change and Ozone Depletion). However, they resulted even 2–3 times higher for Particulate Matter and Mineral and Fossil Resources Depletion. Instead, when soil texture differed, dissimilarities were considerably higher. For example, Climate Change impact category ranged between −46.2% and +108.1% of the identified baseline case (with sandy and clay soils, respectively).