Biogas potential from a green biorefining concept

Lübeck, Mette

Salces, Beatriz Molinuevo

Santamaria-Fernandez, Maria

Uellendahl, Hinrich Wilhelm

Santamaria, Maria

Molinuevo-Salces, Beatriz

Uellendahl, Hinrich

Organic Eprints

cCombining protein extraction and anaerobic digestion to produce feed, fuel and fertilizer from green biomass –An organic biorefinery conceptM. Santamaría, B. Molinuevo-Salces1, M. Lübeck and H. Uellendahl*.Section for Sustainable Biotechnology, Aalborg University Copenhagen, A.C. Meyers Vænge 15, 2450 København, Denmark.*Corresponding author. Tel. +45 9940 2585, E-mail address: hu@bio.aau.dkAcknowledgements: The Organofinery project is supported from "Green Development andDemonstration Program (GUDP) under the Danish Ministry of Food“ and it is part of the OrganicRDD-2 program, coordinated by ICROFS. Crude protein content in the concentrate is around 40% (dry matter basis). Amino acid profile of protein concentrate comparable with current organic poultry feed.THE PROTEIN CONCENTRATE –ORGANIC POULTRY FEED Press cake and brown juice after protein extraction accounted for more than 90% of fresh biomass with 61-81% of VS found in the press cake and 7-11% of VS in the brown juice –energy potential for biogas production. Recovery of crude proteins in the protein concentrate was more than 15%.Figure 1. Separation of total mass, VS and crude protein into the output fractions.ORGANOFINERY CONCEPT – SEPARATION EFFICIENCIES020406080100FreshweightVolatilesolidsCrudeProteinFreshweightVolatilesolidsCrudeProteinSeparation efficiency (%)Press cake Brown juice Protein concentrateRED CLOVER CLOVER GRASSSeparationBiogasplantFermentationBIOGAS POTENTIAL RECOVERYFigure 4. Methane yield of the fresh biomass (m3/t) and of the residualbiomass fractions after the biorefinery process (m3/t of fresh crop). Up to 85% of the methane potential of the fresh crops is stillpreserved in the residual fractions after protein refining (Fig. 4). 41-69% of the potential methane of the fresh crop isrecovered in the press cake. 10-16% of the potential methane of the fresh crop isrecovered in the brown juice. The digestate will be used as organic fertilizer.0501001502002503003504000 10 20 30 40 50 60mL-CH4/g-VSdaysRed clover - Fresh Red clover - Press cake Clover grass - Fresh Clover grass - Press cakeFigure 2. Specific methane yield (mL-CH4/g-VS) during 55 days of AD.Figure 3. Specific methane yield (mL-CH4/g-VS) of brown juice after 15 and 55 daysof anaerobic digestion for 2 different substrate loadings (S/I ratio of 1 and 0.5).010020030040050060015 days 55 days 15 days 55 daysmL-CH4/g-VSHigh organic loading Low organic loadingRED CLOVER CLOVER GRASS The specific methane yield of the press cake from red clover andclover grass was 70% and 90% of the fresh biomass (331 and344 ml-CH4/g-VS), respectively). The press cake presented enough nutrients to ensure asuccessful anaerobic digestion. High specific methane yield of brown juice due to high content of easily degradable organic matter. Low pH (4-5), may need pH control. Some substrate inhibition at high substrate loading.SPECIFIC METHANE YIELDS0102030405060m3 CH4/tFresh crop Press cake Brown juiceRED CLOVER CLOVER GRASS1Present address: IMDEA Energy, Avda. Ramón de la Sagra 3, 28935 Móstoles, Madrid (Spain).

Combining protein extraction and anaerobic digestion to

produce feed, fuel and fertilizer from green biomass –

An organic biorefinery concept

Organically grown green biomass (red clover, clover grass) was investigated as a resource for organic feed and organic fertilizer by combination of proteins extraction and anaerobic digestion of the residues. Extraction of proteins from both crops revealed very favourable amino acid composition for the use as animal feed. The residual 90% of organic matter, leaving the separation as solid press cake and brown juice was subjected to anaerobic digestion to produce biogas and fertilizer. Methane yields of 220-310 and 430-540 ml CH4/g VS were obtained for press cake and brown juice, respectively. No inhibition was detected but the adaptation of microorganisms in the case of the press cake and the substrate overload in the case of the brown juice played a major role for efficient conversion of both fractions during the anaerobic digestion process

Combining protein extraction and anaerobic digestion to produce feed, fuel and fertilizer from green biomass – An organic biorefinery concept

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