Methanogenic potential of biomass from roadside verges preserved with various additives

Abstract

The aim of the present research was to evaluate the chemical composition and storage capacities, as well as the efficiency and composition of biogas from biomass collected from roadside verges. The biomass was collected in July and October and then preserved in microsilos (10L) with and without formic acid, bacterial inoculant, bacterial-enzymatic preparation, enzymatic preparation. After 180 days of storage, biomass samples were analyzed for chemical composition, organic dry matter (ODM) losses and biogas and methane yield (Oxi‐Top Control). Biomass from the summer period had a higher (p<0.01) content of dry matter, neutral detergent fiber, hemicellulose and cellulose and a lower (p<0.01) content of ether extract and acid detergent fiber. Loss of organic matter during preservation and biomass storage © UNIVERSITY OF WARMIA AND MAZURY IN OLSZTYN INTRODUCTION Energy production from renewable sources is a key issue in environmental protection and balanced development of manufacturing and services (Stelmach et al. 2010). The recent development of small agricultural biogas stations has resulted in plant biomass becoming a precious raw material. Cultivated plants which are most frequently used as substrates in biogas production include corn, rye, triticale and sugar beet (Mikołajczak et al. 2009). However, biomass production from these plants for energy purposes is connected with excluding significant areas of arable land from food production (Gołaszewski 2011). Potential sources of substrates for agricultural biogas stations can be waste produced during maintenance of green areas, including biomass from roadside verges that comprise grass, weeds and leaves falling from roadside trees (Pieƒkowski 2010). Production of biogas from this biomass facilitates utilization of this waste and solves the problem of its management. The aim of the present research was to evaluate the chemical composition and storage capacities, as well as the * Presented at the Fourth International Environmental Best Practices Conference, 8-12 September 2013, Olsztyn, Poland Purwin et al. Biogas from roadside verges biomass 19 potential for biogas production from biomass collected from roadside verges in summer and autumn. MATERIALS AND METHODS Biomass from roadside verges was collected with a mower in summer (July) and autumn (October). It was then ground into strand with a theoretical length of 12mm. This biomass was then placed in plastic microsilos (10L), sealed with silicone and equipped with a valve to release fermentation gases. Every trial was repeated three times. After compacting, microsilos were weighed so as to gain an identical degree of densification of a given biomassmaterial. Organic drymatter (ODM) losses were estimated on the basis of the mass of microsilos’ content and ODMconcentration before sealing and after 180 days of storage. Biomass was stored: 0 – without additives; A – with the addition of 96% formic acid, 5g·kg-1 of fresh material; B – with fermentation stimulator in a dose of 5x107CFU including: Lactobacillus plantarum KKP/593/P, L. plantarum KKP/788/P, L. brevis KKP 839, L. buchneri KKP 907; C – with 0.005g·kg-1 endo-1,4-beta-glucanase 100 JCMC, endo-xylanase 100 JX and fermentation stimulator in a dose of 5x107CFU including: L. plantarum KKP/593/P, L. plantarum KKP/788/P, L. brevis KKP 839, L. buchneri KKP 907; D1 – with 0.004g·kg-1 beta-glucanase 300 JCMC, endo‐xylanase 300 JX, glucoamylase 1500 JGA; D2 – with 0.004g·kg-1 hemicellulose and cellulose with the activity of 94 I.U. The chemical analysis of biomass included: basic chemical composition according to standard methods (AOAC 2005), the content of water soluble carbohydrates (WSC) with Anthrone Method (Thomas 1977), fractions of structural carbohydrates: neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) were identified with ANKOM220, the content of hemicellulose was estimated as the difference of NDF-ADF, whereas the content of cellulose as the difference of ADF-ADL (Van Soest et al. 1991). The research of biogas potential of stored biomass was conducted in the Department of Environmental Protection Engineering, University of Warmia and Mazury in Olsztyn (Poland). The biomass was ground mechanically with a cutting mill ROBO 3000 for medium-size 2–3mm particles. Respirometric measurements were conducted with Oxi–Top Control sets. The amount of the batch material of a particular biomass used for respirometric measurements was estimated on the basis of its dry matter (DM) content as well as organic dry matter (ODM). The measurements were conducted at 35°C, the time span was 40 days. The sets were implanted with a batch from the anaerobic reactor designed to decompose plant substrate. The batch was „starved” before conducting respirometric measurements. The content of methane in biogas was provided in volume percentage (%v/v). The amount of produced biogas and methane was provided in normalized values, i.e. in normal liters (LN) per kilogram (kg) of organic dry matter (taking a normalized unit of gas volume LN or m3 in normal conditions, i.e. pressure=1013.25mbar, temperature=0°C, humidity=0%.