Contents lists available at ScienceDirect Biomass and Bioenergy journal homepage: www.elsevier.com/locate/biombioe Research paper Infuenceofdouble-cutharvestsystemonbiomassyield,qualityandbiogas production from C4 perennial grasses Marta Kupryś-Caruk a,∗ , Sławomir Podlaski b , Danuta Kotyrba a a Prof. W. Dąbrowski Institute of Agricultural and Food Biotechnology, Department of Fermentation Technology, Rakowiecka Str. 36, 02-532, Warsaw, Poland b Warsaw University of Life Sciences, Department of Plant Physiology, Nowoursynowska Str. 159, 02-776, Warsaw, Poland ARTICLEINFO Keywords: Cordgrass Big bluestem Switchgrass Methane Silage ABSTRACT Thisstudy'saimwastodeterminetheimpactoftwoharvestsperyearontheyield,biomassquality,andsuit- ability for ensiling and biogas production of cordgrass (Spartina pectinata Bosc ex Link), switchgrass (Panicum virgatum, var.Dacotah)andbigbluestem(Andropogon gerardii, var.Bison).Grasseswereharvestedattheendof June(Iharvest)andatthebeginningofOctober(IIharvest).SingleharvestatthebeginningofOctoberwasalso conducted.BiomassfromIandIIharvestwasensiledandthensubjectedtoanaerobicdigestion.Therewereno diferences between dry matter yield of investigated grasses from I and a single harvest, which indicated the validityoftwoharvestsperyearinordertoincreasebiomassyieldduringagrowingseason.Double-cutharvest system had an efect on C/N ratio and lignin content decreasing in the biomass compared to a single harvest. Biomass from I and II harvest was suitable for ensiling. Double-cut harvest system did not infuence on biogas yield from switchgrass and big bluestem. Cordgrass and big bluestem have been found to be better feedstock than switchgrass for biogas production in Polish climate conditions because they ofered higher methane yield per hectare. 1. Introduction Second-generation biofuel obtained from lignocellulose biomass constitutes an alternative feedstock for biogas production, avoiding land-use competition for feed and food production. Lignocellulose biomass,suchasenergycrops,donotneedhighinputofenergy,water, fertilizers, and pesticides, which makes them a promising material for liquid, solid and gaseous biofuels production [1]. Some warm-season grasses, such as switchgrass, big bluestem or cordgrass, that is char- acterizebyC4photosyntheticpathway,havepotentialinmeetingthese requirements. These grass species are originated from Northern America, but their high biomass yield can be achieved in European climatetoo,asitwasprovedinmanypreviousstudies[2–5]. High biomass yield, as well as high specifc methane yield, is parameters important when choosing the most appropriate crops for biogas production [6]. The biomass intended for biogas production should also be suitable for preservation, mainly through the ensiling process in order to ensure a sustained supply of the feedstock to a biogasplantdigester.Ensilinghasbeenconsideredasafeasiblemethod forpreservingthemethaneyield[7]. Chemical composition of silages, whichafectsthebiodegradabilityandspecifcmethaneyield,hastobe considered when choosing crops for biogas production [8]. Oneofthefactorswhichinfuencetheplantschemicalcomposition isthedegreeofplantsmaturityduringharvest.Thebiomassconducted forcombustionisharvestedinlatewinterorspring,whenthemoisture is low, as well as the concentration of critical elements, such as ni- trogen,ash,K,Cl[9]. Diferent biomass composition is required when taking into account anaerobic digestion (AD), as a result of which biogas (mixture of CH 4 and CO 2 ) is produced [10]. For biogas pro- duction biomass from a ‘green’ harvest is more preferable. To obtain highbiogasyield,feedstockneedstohaveahighcontentofeasilyde- gradable components, such as water-soluble carbohydrates (WSC), so- lublecellcomponents,andlowlignincontent[8].Biomassfromgreen harvest seems to be more suitable for biogas production, but early harvest might result in problems related to ensiling of wet green bio- mass, causing unwanted spoilage of silages and too much dry matter loss[11]. Littlehasbeenfeaturedsofarabouttheutilityofperennialgrasses, two harvests per year, especially the frst harvest conducted in early summer and the impact of two-harvest system on the regrowth char- acteristic. Research concerning ensiling of C4 perennial grasses in- tendedforbiogasproductionhasbeenlimitedaswell.Themainfeed- stockusedforbiogasproductioninagriculturalbiogasplantsoperating in the EU is maize silage and agri-waste, while the use of perennial https://doi.org/10.1016/j.biombioe.2019.105376 Received8March2019;Receivedinrevisedform25July2019;Accepted18September2019 ∗ Corresponding author. E-mail address: marta.kuprys@ibprs.pl (M. Kupryś-Caruk). Biomass and Bioenergy 130 (2019) 105376 0961-9534/ © 2019 Published by Elsevier Ltd. T