Energy Consumption And Greenhouse Gas Emissions Of Straw Disposal And Its Influence Factors

Straw disposal is an important part of rural environmental management.Straw disposal will not only affect the energy consumption of the planting system and greenhouse gas emissions,but also affect the crop yield and the sustainable utilization of farmland.Because of differences in geographical conditions,planting tradition,management mode,land management mode and straw disposal policy,there are great variances in the behavior of straw disposal.It is of research and practical significance to analyze the energy consumption and greenhouse gas emissions and their influence factors under different treatments of straw.In this study,409 households of six cities in Jiangsu province were interviewed by a one-to-one questionnaire,and the input data of rice and wheat rotation system planting and straw disposal were obtained.Based on the process parameters of the life cycle inventory in China and the field investigation data,the life cycle analysis model of rice wheat planting system was constructed.The differences in energy consumption and greenhouse gas emissions under different straw disposal scenarios(return-to-field,burning and removal),different regions(northern,central and southern Jiangsu),and different planting scale were compared.The main factors affecting the energy consumption and greenhouse gas emissions of rice and wheat were analyzed by multiple linear regression models.The results showed that the average energy consumption of rice planting system in Jiangsu province was 1490.29 J/kcal,and the greenhouse gas emissions were 332.90 mg CO2-eq/kcal;the energy consumption of wheat planting system was 1609.12 J/kcal,and the greenhouse gas emission was 276.20 mg CO2-eq/kcal.The energy consumption and greenhouse gas emissions of rice and wheat planting system were compared under different straw disposal scenarios.The energy consumption of straw returning was medium(rice:1486.96 J/kcal;wheat:1589.07 J/kcal),and greenhouse gas emission was least(rice:331.63 mg CO2-eq/kcal;wheat:272.23 mg CO2-eq/kcal).The energy consumption of the removal scenario was the maximum,about 1.2-1.5 times that of return-to-field,and energy consumption of the burning scenario was the least,about 0.8 times that of the return-to-field;the greenhouse gas emissions of the burning scenario was the maximum,about 1.8-2.8 times that of return-to-field;the greenhouse gas emissions of the removal scenario was the next,about 1.3-1.6 times that of the returnto-field.In addition,the study found that although the energy consumption and greenhouse gas emissions of straw disposal in the whole life cycle was not high(0.9%7.1%),the disposal of straw had an important impact on the fertilizer and pesticide input.Return-to field caused the energy consumption and greenhouse gas emissions in spraying insecticide were higher than other scenarios,indicating the return-to-field may cause significant increase in diseases and insect pests.The removal increased the input of chemical fertilizer,thus the energy consumption and greenhouse gas emissions at this stage were higher than other scenarios.Further analysis of the factors affecting the energy consumption and greenhouse gas emissions of rice and wheat planting systems,region and scale significantly did.Specifically,in the rice planting system,the maximum energy consumption and greenhouse gas emissions was in northern Jiangsu(1970.30 J/kcal;401.49 mg CO2eq/kcal),southern and central Jiangsu was smaller,about 0.6-0.8 times of northern Jiangsu.As the scale of rice grows larger,the energy consumption and greenhouse gas emissions of the production units are reduced.The energy consumption and greenhouse gas emissions of wheat were only affected by regional differences.In wheat planting system,the energy consumption and greenhouse gas emissions in southern Jiangsu are the largest(1960.12 J/kcal;356.53 mg CO2-eq/kcal),the second in northern Jiangsu,the smallest in the central Jiangsu,only about 0.6 times of Southern Jiangsu.Planting scale had no significant effect on energy consumption and greenhouse gas emissions of wheat.Based on the above results,the policy recommendations put forward in this study include:1.Use soil testing and other ways to avoid excessive chemical fertilizer application,to reduce the energy consumption and greenhouse gas emissions of it,as the main contributor.2.From the perspective of energy consumption and greenhouse gas emissions,straw returning policy should be pursued properly.Avoiding the increase of disease and insect pests caused by excessive return-to-field reduces energy consumption and greenhouse gas emissions.3.Large-scale cultivation should be encouraged to reduce per unit energy consumption and greenhouse gas emissions in the production of rice.The innovation of this study was to obtain the actual behavior data of farmers by large-scale and accurate survey,to evaluate the energy consumption and greenhouse gas emissions caused by rice and wheat production in Jiangsu province.Based on the traditional life cycle analysis,depending on the statistical analysis method,the factors that affect the energy consumption and greenhouse gas emissions were analyzed.The insufficiency of this study was that the proportion of straw burning and removal in the province is greatly reduced by the strict implementation of the straw returning policy in Jiangsu Province,and the sample size of these is small,which may have a certain impact on the evaluation results.