Ecological Sustainability in "Energy Return on Investment (EROI) "and its Correlation with Agricultural Landscape Heterogeneity (Case Study: Qazvin Province)

The problem of energy efficiency is one of the key pillars of economics, especially agricultural sector. In term of energy efficiency, a similar estimation for human actions and their consequents can be applied to the landscape system, which first introduced by Hall et al. (1986), and now referred to Energy Return on Investment (EROI). Many energy analyzes have been done, take into account a social system boundary and an input and output approach. This approach will inevitably hide the system's internal performance inside a black box. Recently, Tello et al. (2016) have proposed a novel approach for analyzing energy at the agricultural landscape scale with the aim of evaluating energy sustainability under multiple EROIs that views the landscape as a set of energy cycles between nature and society.The proposes of this study have been to consideration the theory and methodology of multiple EROIs, to investigate the efficiency of energy flow in Qazvin agricultural landscape and, to examine the relationship between energy efficiency and landscape heterogeneity in order to describe the interaction of landscape structure and energy efficiency.

The database of this case study was prepared from 46 counties of Agricultural Organization of Iran and land use map. Agricultural database was created based on agriculture, livestock, and pasture subsystems. Agricultural yield for each crop, number of agricultural, and horticultural labors, number and type of agricultural machinery, amount of fertilizers, herbicides and fungicides, used fossil fuels, electricity, and agricultural waste belonged to the agricultural sub-sector. Census of livestock, livestock and poultry production, livestock and poultry feed, livestock and poultry production, workers and machinery, fossil fuel and electricity needed and livestock waste were collected for the livestock sector. Pasture production used for livestock grazing, amount of livestock manure going back to rangelands were belong to pasture sector.All energy flows were converted to gross caloric value following research by Guzmán et al. (2014). In this method, the calculation of multiple EROIs has replaced the conventional methods of energy efficiency calculation. Landscape heterogeneity calculated using landscape metrics. Correlation coefficient was performed using SPSS between EROIs and heterogeneity.

The highest value of FEROI was found in Bashariyate Sharghi with 0.25 and the lowest was in Kharghane Gharbi with 0.018. EFEROI, which is the most similar to the conventional method of energy efficiency, had the highest rate with 0.666 in Bashariate Gharbi and the lowest rate with 0.020 in Kharqan Gharbi. IFEROI was 0.95 in Narjah and the lowest was in Shahidabad with 0.168. Lower IFEROI indicates a higher return biomass in the production system, which seeks to maintain reproduction in the system by closing the biophysical cycles. The highest NPPEROI were reported by Bashariate Gharbi at 1.122 and lowest by Kharqan Gharbi at 0.173.In this study the relationship between the EROIs index and the heterogeneity of the landscape structure was shown. The results have showed the inverse correlation between heterogeneity and energy efficiency, indicating the heterogeneous impact of landscape structure on these indicators. It can be deduced that the heterogeneity created by human in Qazvin province has reduced energy efficiency. To explain this inverse correlation between energy efficiency and the heterogeneity of the landscape, it should be noted that one of the factors affecting efficiency is that may final production come from land uses that needed more input energy and produce less output. By examining the relationship between these indices with land use and land cover of each county, it was found that these indices had their lowest level in dry farming. It means that in Qazvin province, energy efficiency in dry farming is low, and relay on external inputs, which was mainly fossil fuel.

This study has explained how the calculation of several energy efficiency coefficients provides more complete information than conventional methods for decision making. The results of this study can be applied in land use planning to integrate energy considerations in planning and comprehensive agricultural development plan.