Microbial biogas production from hydrolysis lignin: Insight into lignin structural changes

Background: The emerging cellulosic bioethanol industry will generate huge amounts of lignin-rich residues that may be converted into biogas by anaerobic digestion (AD) to increase the output of energy carriers from the biorefnery plants. The carbohydrates fraction of lignocellulosic biomass is degradable, whereas the lignin fraction is generally considered difcult to degrade during AD. The objective of this study was to investigate the feasibility of biogas production by AD from hydrolysis lignin (HL), prepared by steam explosion (SE) and enzymatic saccharifcation of birch. A novel nylon bag technique together with two-dimensional nuclear magnetic resonance spectroscopy, pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS), and Fourier transform infrared (FTIR) spectroscopy was used to identify recalcitrant and degradable structures in the lignin during AD. Results: The HL had a lignin content of 80% which included pseudo-lignin and condensed-lignin structures resulting from the SE pretreatment. The obtained methane yield from HL was almost twofold higher than the theoretical methane from the carbohydrate fraction alone, indicating that part of the lignin was converted to methane. Characterization of the undegradable material after AD revealed a substantial loss of signals characteristic for carbohydrates and lignin–carbohydrate complexes (LCC), indicating conversion of these chemical components to methane during AD. The β-O-4′ linkage and resinol were not modifed as such in AD, but major change was seen for the S/G ratio from 5.8 to 2.6, phenylcoumaran from 4.9 to 1.0%, and pseudo-lignin and condensed-lignin were clearly degraded. Scanning electron microscopy and simultaneous thermal analysis measurements demonstrated changes in morphology and thermal properties following SE pretreatment and AD. Our results showed that carbohydrate, LCC, pseudo-lignin, and condensed-lignin degradation had contributed to methane production. The energy yield for the combined ethanol production and biogas production was 8.1 MJ fuel per kg DM of substrate (4.9 MJ/kg from ethanol and 3.2 MJ/kg from methane). Conclusion: This study shows the beneft of using a novel bag technique together with advanced analytical techniques to investigate the degradation mechanisms of lignin during AD, and also points to a possible application of HL produced in cellulosic bioethanol plants.publishedVersio

Evaluación técnica-ambiental de un sistema de micro-cogeneración basado en gas natural para aplicación residencial

The study carried out here aims to determine the advantage of using in-situ electricity generation facilities versus conventional generators, being evaluated from the environmental point of view. For this, an environmental analysis on the production of CO2 has been applied to two scenarios of electricity generation for a residential building in Medellin city (Colombia). The first one refers to La Sierra thermo-electric plant located in La Sierra, municipality of Puerto Nare, in the Antioquiashire, which is the most efficient plant in Colombian thermal generation. The second comparison scenario refers to the annual operation of a micro-cogeneration facility, which satisfies the building's hot water and electrical energy needs. Using the capabilities of the TRNSYS v17® energy simulation software and the emission equations available in the public domain, the comparative environmental analysis is carried out between one and the other for the same load. The losses in electric transmission are assumed to be 10%. This analysis has shown a difference of more than 50% in emissions generation, with the main cause being the amount of fuel used, which for both cases is natural gas. On the other hand, this study shows the environmental advantages in the use of in-situ generators, decreasing transmission losses.Evaluación técnica-ambiental de un sistema de micro-cogeneración basado en gas natural para aplicación residencialpublishedVersio

Inherent properties of Scots pine forest residues harvested in South Norway

Biomass from forestry sector is able to provide an important contribution to meet the government’s targets for increasing bioenergy use. Traditionally it has been stem wood which is used as raw material for energy. For a deeper understanding of trees, knowledge is required not only of the stem wood, but also of the branches and tree tops. Research complex on Norway's industrially important tree species - Scots pine (Pinus sylvestris L.) forest residues (stem wood, stem bark, branches, top of trees) moisture content, basic density and effective heating value were analysed in 2 sampling plots, depending on site index quality in South Norway forest. The vertical dependence of bark proportion was observed. The pattern was similar for both site indexes, lower bark content in the bottom part of stem, slightly increasing approximately to 35 % of the tree height and so increasing towards the tree top. The vertical dependence of bark thickness of Scots pine trees showed an increasing trend towards the top. Bark was significantly thicker near the base than near the top. Bark proportion may be a relevant aspect for the utilization of Scots pine forest residues as potential biomass feedstock. Considerable variations in qualitative properties between stem wood, stem bark and branch wood of Scots pine along the stem were observed. The basic density of stem wood was in range 308.2-418.3 kg/m3, of stem bark 265.1-364.2 kg/m3 and of branch wood 400.5-579.2 kg/m3. The basic density of stem wood was higher in the lower part of stem, vertically decreasing towards to tree top. Contrary, the basic density of stem bark decreased to 40 % height and then slightly increasing again towards the top. The axial dependence of basic density in stem bark was different than the one in stem wood, more regular. Branch density decreased moderately within the axial direction along the crown. Scots pine branch wood exanimated in this study was denser in the bottom part crown towards less denser branches positioned in the top crown section. More else a clear variation pattern was apparent in basic density variations along the branch. Density declined from the branch base outward first rapidly and then levelled. The highest basic density was found for the branch base. There was not found relationship between basic density of stem wood, stem bark, branch wood and site index quality of stands. The average moisture content of stem wood and stem bark harvested in early spring season increased axially from the base toward tree top, within significantly more pronounced variations on the tree base compare to tree top. Stem bark had relatively higher moisture content compare to stem wood. The moisture content in stem wood was in range 39.9-90.2 %, in stem bark 42.8-94.3 % and in branch wood 43.5-62.8 %. The effective calorific value of stem wood was in range 5.09-5.40 kWh/kg, of stem bark 5.11-5.51 kWh/kg and of branch wood 5.16-5.49 kWh/kg. The vertical dependence trend of effective calorific value for Scots pine stem wood was similar to that for stem bark. Regular decreasing pattern towards the top was observed. We observed significantly higher calorific value at level p<0.05* in stem bark than in stem wood. Elevated effective calorific value of stem bark and branch wood make these materials a valuable industrial energy source for bioenergy in Norway

Characterization of Ashes from Pinus Sylvestris forest Biomass

Efficient and profitable biomass combustion is often limited by ash related operational problems. Knowledge of the ash melting and sintering is of important, in terms of predict and reduce ash-related problems in biomass-fired boilers. In this study, chemical composition and melting behaviors of ashes from the four parts of P. sylvestris trees were investigated. The four parts from Pinus sylvestris trees are stem wood, bark, branch base and twigs. A simultaneous thermal analyzer (STA) was used to characterize the melting behavior of selected biomass fuels in oxidizing atmosphere. Ash melting process was identified as the distinctive endothermic peaks on recorded DSC curves. The results showed that the stem wood of pine contains higher contents of most of the ash forming matters than other tree parts. Chemical composition of ashes from four parts of the pine tree is dominated by element Ca, K, Mg, Mn, P and Si. The K, Na and P contents in the twigs are significantly higher than that of stem wood, bark, and branch base indicating high tendency of ash melting and slagging. STA experiments indicated that the melting process of the studied fuel ashes start in the temperature range of 930-965 °C. Scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometry (EDX). Analyses results showed that the stem wood ash remains loose structure even after 1000 °C sintering treatment. But the ashes originated from top branch show sign of sintering at 1000 °C. The obtained results of present work can be considered as useful information within an industry interest for a prediction of the forest biomass ash melting behavior

Solid biofuels from forest – fuel specification and quality assurance - Inherent properties of Norway spruce biomass in some geographical locations in South Norway

Biomass from forestry sector is able to provide an important contribution to meet the government’s targets for increasing bioenergy use. Traditionally it has been stem wood which is used as raw material for energy. For a deeper understanding of trees, knowledge is required not only of the stem wood, but also of the branches and tree tops. The most important fuel qualitative properties of stem wood, bark, branch wood and tree tops were investigated in order to know the potential of Norway spruce biomass available for bioenergy use in Norway.publishedVersio

Klimagassutslipp i skogbruket - fra frø til industriport. Vugge-til-port livsløpsanalyse (LCA). Prosjektrapport fra KlimaTre

Klimaendringer har vært sterkt i fokus den siste tiden, både nasjonalt og internasjonalt. Det er derfor økende interesse for fornybare energikilder fra forskjellige hold. Økt høsting av biomasse til industri- og energiformål fører til økt energiforbruk og dermed økte CO2-utslipp. Ved hjelp av en livsløpsanalyse (Life Cycle Assessment - LCA) kan man beregne klimagassutslipp fra skogbruket. Enkeltfaktorer som bidrar mest til klimagassutslippene kan identifiseres i analysen og forhåpentligvis forbedres. Prosjektet KlimaTre har som hovedmål å dokumentere de skogbaserte verdikjedenes betydning for klima og verdiskaping i Norge. Denne rapporten er en leveranse i delprosjekt KlimaVerdi og presenterer resultatene fra en livsløpsanalyse (LCA) av de prosessene som inngår i skogbrukets forsyningskjede fra frø til industriport (fra vugge til port). Det presenteres beregninger for årlige klimagassutslipp (klimaregnskap) og annen miljøpåvirkning fra frøproduksjon via ulike skogkulturprosesser til avvirkning og tømmertransport. Klimagassutslipp er beregnet som CO2-ekvivalenter per kubikkmeter tømmer som ble avvirket i 2010. Det samlede klimagassutslippet fra produksjonen av 8,4 millioner m3 tømmer til industrielle formål var på 150 000 tonn CO2-ekvivalenter i 2010, eller 17,85 kg CO2-ekvivalenter per produsert kubikkmeter tømmer levert ved sagbruk/fabrikk. Dette utgjør 2,4 % av det CO2 som bindes av 1 m3 tømmer. Transport med lastebil bidro mest til det samlede klimagassutslippet (nesten 50 %), fulgt av sluttavvirkning (32 %) og tynning (9 %). Leveranse til lokale sagbruk reduserer transportavstandene og dermed CO2-utslippet, mens økende sentralisering og nedleggelse av treforedlingsindustrien fører til større transportavstander og dermed CO2-utslipp. Utvidet transport av tømmer på jernbanen vil kunne bidra til å redusere CO2-utslippene.publishedVersio

Innovativ utnyttelse av aske fra trevirke for økt verdiskaping og bærekraftig skogbruk (askeverdi)

I de kommende årene forventes det en økende satsing på etablering av biobrenselanlegg i Norge. Økt forbrenning av trebasert biobrensel vil også medføre økt produksjon av betydelige mengder aske som må håndteres på en hensiktsmessig måte. En bærekraftig utnyttelse av de resulterende askeressursene fra biomassen blir derfor stadig viktigere. Treaske har en varierende sammensetning, men inneholder det meste av de viktige næringsstoffer og tungmetaller som fantes i trevirket før forbrenningen. Asken er meget alkalisk. Anvendelse av aske i jordsmonn øker pH-verdien og innholdet av de fleste hovednæringsstoffene, samt at tilgjengeligheten av sporelementer (tungmetaller) reduseres. Aske fra trevirke med riktig kvalitet kan derfor utnyttes i forvaltningen av forsuret grøntarealer, jordbruksarealer eller områder med flatehogst som trenger kalktilsetning. Askeegenskapene avhenger av hvilken type biobrenselsortiment som benyttes i forbrenningen, riktig styring av prosessparametre i forbrenningsprosessen, samt behandling og lagring av askene. Alle askene i denne undersøkelsen er fra biobrenselanlegg med ristovner. Undersøkelsene i denne studien viste at den kjemiske kvaliteten på de ulike treaskene varierte betydelig, avhengig av faktorer som kvaliteten på biobrenselet som benyttes til forbrenningen, treslag, biobrenselsortiment og type forbrenningsanlegg. I tillegg vil faktorer som lagring, håndtering og forbrenningstemperatur ha betydning for askekvalitetene som oppnås. For bestemmelse av askens kjemiske kvalitet er det viktig å evaluere alle elementer (næringsstoffer og tungmetaller). Analysene viser at det var en oppkonsentrasjon av tungmetaller i flyveaskene, sammenlignet med bunnaskene undersøkt i denne studien. De laveste nivåene av organisk karbon ble målt i bunnaskene, noe som indikerer at forbrenningsforholdene var gode i perioden for prøvetakingen. Det ble målt et høyere silisiumnivå i noen av bunnaskene. Silisiumnivået i aske fra biobrensel som inneholder bark kan være høyt på grunn av sand, grus og andre forurensninger som tas opp under tømmerhogst og transport. Det kan undersøkes om disse biobrenselanleggene er mer utsatt for sintring og slagging på forbrenningsristen. Konsentrasjonen av klor og svovel i alle undersøkte flyveasker var mye høyere enn i bunnaskene. Klor og svovel vil kunne ha en korrosiv effekt på forbrenningsanleggets komponenter, og er medvirkende elementer ved sintring og slaggdannelse. I Norge er tilbakeføring av aske til skog ikke tillatt fordi «Forskrift om gjødsel varer mv. av organisk opphav (2003)» ikke definerer skog som et av arealene det kan spres aske på. Forskriften er på tiden under revisjon. En av bunnaskene som ble undersøkt hadde høyt innhold av næringsstoffer, lave konsentrasjoner av tungmetaller, lite uforbrent organisk karbon og en høy pH-verdi. Med hensyn til resirkulering vil denne asken kunne anvendes i grøntarealer og jordbruksarealer. Denne asken ble derfor valgt ut til et feltforsøk i skog som startet opp i mai 2013. Bruk av aske fra biobrenselanlegg som gjødsel i Norge bør så raskt som mulig få en høyere prioritet på den politiske dagsordenen. For å komme videre er det viktig at ulike industri- og næringsaktører innenfor områdene bioenergi, skogbruk, varmedistribusjon, miljøvernmyndigheter m.fl. deltar aktivt i utformingen av et anvendelig regelverk

Heating Value and Ash Content of Downy Birch Forest Biomass

Biomass from forestry sector provides an important contribution to meet the government's targets for increasing bioenergy production and utilization. Characterization of forest residues is critical for exploiting and utilizing them for energy production purpose. In present work, stem wood, stem bark, branches, top of trees from downy birch forest were sampled from different sites in South Norway and subjected to heating value and ash content measurement. Properties of different parts of trees vertically along the tree trunk and radially along the branch and crown level were assessed via the statistical model. The heating value of stem wood was in range 18.14-18.57 MJ/kg, of stem bark 18.50-18.72 MJ/kg and of branch wood 18.21-18.50 MJ/kg. The vertical dependence of heating value of downy birch stem wood was similar to that of stem bark. Regular decreasing of heating value towards the tree top was observed. Significantly higher heating value at level p&lt;0.05∗of stem bark than the one of stem wood was observed. The ash content of downy birch branch wood did vary axially along the branch whereas there are only slight differences of ash content of branch within the crown. The stem bark has the highest ash content in range 2.0-2.5%, followed by branch wood in range of 1.0-1.6% and the lowest for stem wood in range of 0.3-0.5%

Solid biofuels from forest – fuel specification and quality assurance - Inherent properties of Norway spruce biomass in some geographical locations in South Norway

Biomass from forestry sector is able to provide an important contribution to meet the government’s targets for increasing bioenergy use. Traditionally it has been stem wood which is used as raw material for energy. For a deeper understanding of trees, knowledge is required not only of the stem wood, but also of the branches and tree tops. The most important fuel qualitative properties of stem wood, bark, branch wood and tree tops were investigated in order to know the potential of Norway spruce biomass available for bioenergy use in Norway