@article{0ec9f32838dc408ea8c314555326d286,

title = "Life cycle assessment of biogas production through anaerobic co-digestion of nopal cladodes and dairy cow manure",

abstract = "\textcopyright 2017 Elsevier Ltd Nopal (Opuntia ficus-indica (L.) Mill.) has the ability to grow in climatic conditions that are adverse for most conventional crops. It can be an alternative for biogas production by co-digestion with dairy cow manure, the second largest source of greenhouse gas emissions in dairy farms. To evaluate the feasibility of using nopal as a biogas source, the environmental impacts associated with the process need to be quantified. In this study, a life cycle assessment is carried out to evaluate the environmental impacts and energy balance of biogas production through co-digestion of nopal cladodes and dairy cow manure. A Baseline and three scenarios that had different farming systems and digestate storage management strategies were compared. Cropping system and direct field emission data were experimentally obtained from two plots using an organic farming system and a conventional farming system; biogas production and yield data were obtained in a 10-L anaerobic digester. Results indicated that the energy return on investment for biogas production ranged from 8.1 to 12.4. Organic farming system decreases the environmental impact by 22.5\% in the global warming potential category but increases the acidification potential and eutrophication potential impact category values by 47.2 and 45\% respectively, while covering the digestate tank results in a 2.3\% reduction in global warming potential and in a 1.7\% reduction in photochemical ozone creation potential. Based on these results, biogas production from nopal cladode and dairy cow manure co-digestion and digestate management offers cleaner energy production since the global warming potential has a lower value than that reported for similar feedstocks. The use of these two biomasses combines the strengths of a plant that accumulates biomass efficiently and the reduction of greenhouse gas emissions by using one of the main wastes in dairy production.",

author = "G.N. Demirer and Goksel Demirer",

note = "Funding Information: This paper is supported by the National Key Basic Research and Development Program of China (973) (Project No. 2012CB720405 ) and the National Nature Science Foundation of Naval University of Engineering (No. HG DYDJJ-13002 ). The authors wish to thank the reviewers for their careful, unbiased and constructive suggestions, which led to this revised manuscript. Appendix A Constraint Mathematical description BF The balance of HM (hot metal) composition ∑ w j , hm = 1 The balance of a certain main element ∑ ( w i , j m j ) = 1000 w i , hm ,i is Fe, P, Mn or S Lower bound of iron ore grade 56 % ∑ m Fe , i ≤ ∑ m Fe , i ⋅ w Fe , i i is the i th iron ore Lower bound of agglomerate ratio 85 % ∑ ( m sp + m pp + m lp ) ≤ ∑ ( m sp + m pp ) Upper bound of coke load 180 ≤ m cp ≤ 500 , kg / t Upper bound of bosh gas index X bgi ≤ 64 . 78 , m / min Upper bound of S load L S ≤ 10 kg / t Upper and lower bounds of H 2 utilization rate 40 % ≤ r H 2 ≤ 50 % Upper bound of S in HM w S , hm ≤ 0.07 % Upper bound of P in HM w P , hm ≤ 0.4 % Upper bound of Mn in HM w Mn , hm ≤ 1.2 % Lower bound of Fe in HM 90 % ≤ w Fe , hm Upper and lower bounds of C in HM 3.5 % ≤ w C , hm ≤ 4.5 % Upper and lower bounds of Fe distribution in HM 99 % ≤ d Fe , hm ≤ 99.75 % Upper and lower bounds of Mn distribution in HM 40 % ≤ d M n , hm ≤ 80 % Upper and lower bounds of S distribution in HM 5 % ≤ d S , hm ≤ 20 % Upper and lower bounds of Ti distribution in slag 85 % ≤ d Ti,slag ≤ 97 % Upper and lower bounds of V distribution in slag 98.5 % ≤ d V , s l a g ≤ 99 % Upper and lower bounds of S distribution in BFG 4.5 % ≤ d S , b f g ≤ 5.5 % Upper and lower bounds of relative efficiency η l ≤ η x ≤ η L , x is the inner or mechanical efficiency of air blower, TRT, turbine or gen Upper and lower bounds of slag basicity 1.15 ≤ R slag ≤ 1.16 Upper and lower bounds of MgO in slag 5 % ≤ w MgO , slag ≤ 12 % Upper bound of Al 2 O 3 in slag w Al 2 O 3 , slag ≤ 20 % Upper and lower bounds of top gas temperature 200 ≤ T bfg ≤ 250 , ° C The heat balance in the high temperature zone Q o u t , h t z ≤ Q i n , h t z The C-O balance in the high temperature zone M C t , h t z ≤ M C d , h t z SP Lower bound of desulfurization rate w S , o u t ≤ 10 % w S , i n Upper and lower bounds of basicity bias 1.8 ≤ R pr ≤ 2.2 Upper and lower bounds of preset sinter basicity − 0.05 ≤ R sp − R pr ≤ 0.05 Lower bound of preset TFe in sinter ore 55 ≤ TFe pr , % Upper and lower bounds of TFe in sinter ore − 0.5 ≤ TFe sp − TFe pr ≤ 0.5 , % Upper bound of FeO in sinter ore w FeO , sp ≤ 9 % Upper and lower bounds of CaO in sinter ore 10 % ≤ w CaO , sp ≤ 11 % Upper and lower bounds of MgO in sinter ore 2 % ≤ w MgO , sp ≤ 2.5 % Upper and lower bounds of Al 2 O 3 in sinter ore 1.5 % ≤ w MgO , sp ≤ 3 % Upper bound of S in sinter ore w S , sp ≤ 0.1 % Adjusted upper bound of P in sinter ore w P , sp ≤ 0.1 % Adjusted upper bound of Si in sinter ore w Si , sp ≤ 5.5 % Upper and lower bounds of material mass m l ≤ m i ≤ m L , i is the i th ore, flux or fuel Upper and lower bounds of mass relation m s l ≤ ∑ m i ≤ m s L Upper and lower bounds of return ratio 30 % ≤ r ro ≤ 35 % Upper and lower bounds of bedding ratio 10 % ≤ r b ≤ 15 % Adjusted upper and lower bounds of bedding rate 10 % ≤ r b,ad ≤ 12 % Upper and lower bounds of H 2 O in mixture 7 % ≤ w H 2 O , m i x ≤ 8 % Upper and lower bounds of air leak 30 % ≤ a leak ≤ 40 % Upper and lower bounds of slag heat ratio 3 % ≤ r slag ≤ 4 % CP Upper and lower bounds of H 2 O in coal 9.5 % ≤ w H 2 O , c o a l ≤ 10.5 % Upper and lower bounds of ash in coal 9 % ≤ w a s h , c o a l ≤ 11 % Upper and lower bounds of volatile in coal 24 % ≤ w v o , c o a l ≤ 31 % Upper and lower bounds of hot coke 950 ≤ T h c ≤ 1050 , ° C Upper and lower bounds of N transform index 12 % ≤ r N ≤ 16 % Upper and lower bounds of O-H 2 O transform index 30 % ≤ r O - H 2 O ≤ 50 % Upper and lower bounds of air leak 10 % ≤ a leak ≤ 25 % Upper and lower bounds of gas leak 8 % ≤ g leak ≤ 10 % PP Upper and lower bounds of H 2 O in mixture 8 % ≤ w H 2 O , m i x ≤ 10 % Upper and lower bounds of return ratio 5 % ≤ r ro ≤ 8 % Upper and lower bounds of slag heat ratio 2 % ≤ r slag ≤ 3 % Upper bound of FeO in pellet ore w FeO , pp ≤ 1 % Lower bound of desulfurization rate w S , o u t ≤ 5 % w S , i n BOF The balance of MS (molten steel) composition ∑ w j , ms = 1 The balance of a certain main element ∑ ( w i , j m j ) = 1000 w i , ms ,i is Fe, P, Mn or S Upper bound of S in MS w S , ms ≤ 0.021 % Upper bound of P in MS w P , ms ≤ 0.020 % Upper bound of Mn in MS w Mn , ms ≤ 0.18 % Upper bound of N in MS w N , ms ≤ 0.008 % Upper bound of T[O] in MS w T [ O ] , ms ≤ 0.003 % Upper and lower bounds of C in MS 0.17 % ≤ w C , ms ≤ 0.18 % Upper and lower bounds of slag basicity 3.49 ≤ R slag ≤ 3.51 Upper and lower bounds of top gas temperature 1450 ≤ T ldg ≤ 1500 , ° C Upper bound of temperature drop of MS T ms,dr ≤ 50 ° C Upper bound of temperature of MS sedation T ms,se ≤ 50 ° C Lower bound of superheat temperature of MS 70 ° C ≤ T ms,drop Lower bound of C transformed into CO in MS 85 ° C ≤ r C - CO Upper and lower bounds of heat loss ratio 3 % ≤ r heatloss ≤ 8 % CC Total water supply of secondary cooling zone Q ˙ water 2 = 2000 L / m i n Lower bound of superheat temperature 20 ° C ≤ T slab Upper and lower bounds of casting speed 1.25 ≤ 60 T slab ≤ 1.35 , m / m i n RP Upper and lower bounds of HC temperature 598 ≤ T HR ≤ 602 , ° C Upper and lower bounds of HC proportion 0.5 ≤ r HR ≤ 1 Upper bound of burning ratio of slab r O b ≤ 1.8 % Upper and lower bounds of surface temperature 1190 ≤ T sur,slab ≤ 1200 , ° C Upper and lower bounds of downward pressing rate 24 % ≤ r down ≤ 34 % Upper and lower bounds of relative coefficient n l ≤ n x ≤ n L , x is the coefficient for eternal stress, tension or motor overload Publisher Copyright: {\textcopyright} 2017 Elsevier Ltd",

year = "2018",

language = "English",

volume = "172",

journal = "Journal of Cleaner Production",

issn = "0959-6526",

publisher = "Journal of Cleaner Production",

}