Anaerobic digestion of microalgae and pulp and paper biosludge

In recent decades, microalgae have attracted attention as a promising biomass source for a variety of different biofuels, including methane via anaerobic digestion (AD). However, the energy intensity and cost (e.g., for the nutrient supply) of the process chain mean that breakthroughs in algal biofuels have yet to be realized. The objective of this study was to improve the AD of wastewater-grown microalgal biomass, marine algal residues following lipid extraction for renewable diesel production and to improve the AD of pulp and paper industry biosludge. The digestate from the latter substrate could provide nutrients for algae cultivation and lipid extraction followed by AD offers the possibility of obtaining multiple products from algal biomass, as envisaged by the algal biorefinery concept.Based on the results of this experimental work, pretreatments and novel reactor designs can be used to improve the AD of microalgae. In this study, BMPs for wastewater- and digestate-grown mixed populations of microalgae varied between 154 and 273 L CH4 kg– 1 volatile solids (VS). Low-temperature (3 h, 80°C) pretreatments enhanced the BMPs by 11–27%. However, to ensure positive energy balances, the availability of waste heat was necessary. Due to longer solid retention times, the AD of microalgae in unmixed, accumulating-volume reactors (AVRs) at 16–21° C was more feasible than AD in conventional completely stirred tank reactors (CSTRs) at 35°C when the solid concentration of the algal biomass was low (In the present study, the AD of marine algae residue after lipids were extracted for renewable diesel production was demonstrated and the salt concentration of the marine algal biomass did not affect AD. Thermophilic AD in the CSTR resulted in a 48% higher methane yield (220 L CH4 kg–1 VSs) of algal residues compared with mesophilic AD. However, unlike mesophilic AD, ammonia, which originated from the high nitrogen content of the algal biomass, inhibited the thermophilic process.AD of pulp and paper industry biosludge mineralized nutrients to a soluble form, making effluent a potential media for algal cultivation. The methane yield from the biosludge was low (78 L CH4 kg–1 VS) but increased by 77% with thermal pretreatment (20 min, 121°C). The pretreatment also resulted in AD with a retention time of 10 d, as compared to 14 d for untreated biosludge. However, the energy balance of the pretreatment was dependent on the solid concentration and temperature of the biosludge from the industrial process.To conclude, this work demonstrated AD of microalgae under psychrophilic, mesophilic, and thermophilic conditions. The low energy balances emphasize that improvements in algae cultivation are required and/or other benefits (e.g., nutrient recovery, value-added products, and waste treatment) obtained for algal AD to become a full-scale application

Ravinnevisio : Selvitys Pirkanmaan puhdistamolietteiden ja biojätteiden ravinteista ja niiden potentiaalisesta käytöstä

Loppuraportti201

Hydrothermal carbonization of pulp and paper industry wastewater treatment sludges - characterization and potential use of hydrochars and filtrates

The pulp and paper industry's mixed sludge represents waste streams with few other means of disposal than incineration. Hydrothermal carbonization (HTC) could be advantageous for the sludge refinement into value-added products, thus complementing the concept of pulp and paper mills as biorefineries. Laboratory HTC was performed on mixed sludge (at 32% and 15% total solids) at temperatures of 210–250 °C for 30 or 120 min, and the characteristics of the HTC products were evaluated for their potential for energy, carbon, and nutrient recovery. The energy content increased from 14.9 MJ/kg in the mixed sludge up to 20.5 MJ/kg in the hydrochars. The produced filtrates had 12–15-fold higher COD and 3–5-fold higher volumetric methane production than untreated sludge filtrates, even though the methane yield against g-COD was lower. The increased value of the hydrochars in terms of energy content and carbon sequestration potential promote HTC deployment in sludge treatment and upgrading.publishedVersionPeer reviewe

Replacing centralised waste and sanitation infrastructure with local treatment and nutrient recycling : Expert opinions in the context of urban planning

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0

Towards the implementation of hydrothermal carbonization for nutrients, carbon, and energy recovery in centralized biogas plant treating sewage sludge

In recent years, extensive experimental research on hydrothermal carbonization (HTC) of sewage sludge has been performed, to study the effects of process conditions on hydrochar characteristics and nutrient, carbon, and energy recovery from sewage sludge. To promote the implementation of HTC, this study assessed HTC (230 °C, 30 min) integration into an advanced centralized biogas plant by analyzing its theoretical effects on the fates of sewage sludge solids, nitrogen, phosphorus, and carbon. The study used the mass and nutrient flows and concentrations obtained from laboratory studies, and the studied biogas plant had an original layout that employed hygienization. HTC integration decreased the solid product volume by up to 56 % and, increased the recovery of ammonium in ammonia water by 33 % and methane by 1.4 %, while increasing the biogas plant energy demand by 4 %. The changes in the nutrient and solids flows and their recovery potentials show the need to consider the rearrangements of the liquid and gas flows in the biogas plant and the re-dimensioning of stripping process.Peer reviewe

Anaerobic digestion of microalgae and pulp and paper biosludge

In recent decades, microalgae have attracted attention as a promising biomass source for a variety of different biofuels, including methane via anaerobic digestion (AD). However, the energy intensity and cost (e.g., for the nutrient supply) of the process chain mean that breakthroughs in algal biofuels have yet to be realized. The objective of this study was to improve the AD of wastewater-grown microalgal biomass, marine algal residues following lipid extraction for renewable diesel production and to improve the AD of pulp and paper industry biosludge. The digestate from the latter substrate could provide nutrients for algae cultivation and lipid extraction followed by AD offers the possibility of obtaining multiple products from algal biomass, as envisaged by the algal biorefinery concept.Based on the results of this experimental work, pretreatments and novel reactor designs can be used to improve the AD of microalgae. In this study, BMPs for wastewater- and digestate-grown mixed populations of microalgae varied between 154 and 273 L CH4 kg– 1 volatile solids (VS). Low-temperature (3 h, 80°C) pretreatments enhanced the BMPs by 11–27%. However, to ensure positive energy balances, the availability of waste heat was necessary. Due to longer solid retention times, the AD of microalgae in unmixed, accumulating-volume reactors (AVRs) at 16–21° C was more feasible than AD in conventional completely stirred tank reactors (CSTRs) at 35°C when the solid concentration of the algal biomass was low (In the present study, the AD of marine algae residue after lipids were extracted for renewable diesel production was demonstrated and the salt concentration of the marine algal biomass did not affect AD. Thermophilic AD in the CSTR resulted in a 48% higher methane yield (220 L CH4 kg–1 VSs) of algal residues compared with mesophilic AD. However, unlike mesophilic AD, ammonia, which originated from the high nitrogen content of the algal biomass, inhibited the thermophilic process.AD of pulp and paper industry biosludge mineralized nutrients to a soluble form, making effluent a potential media for algal cultivation. The methane yield from the biosludge was low (78 L CH4 kg–1 VS) but increased by 77% with thermal pretreatment (20 min, 121°C). The pretreatment also resulted in AD with a retention time of 10 d, as compared to 14 d for untreated biosludge. However, the energy balance of the pretreatment was dependent on the solid concentration and temperature of the biosludge from the industrial process.To conclude, this work demonstrated AD of microalgae under psychrophilic, mesophilic, and thermophilic conditions. The low energy balances emphasize that improvements in algae cultivation are required and/or other benefits (e.g., nutrient recovery, value-added products, and waste treatment) obtained for algal AD to become a full-scale application

Miksi nuorisotyötä tehdään? tietokirja nuorisotyön opetussuunnitelmasta

Miksi nuorisotyötä tehdään? Tietokirja nuorisotyön opetussuunnitelmasta antaa perustaviin kysymyksiin perusteltuja vastauksia. Kirjassa esitetään näkemys nuorisotyöstä kasvatuksellisena prosessina. Se pohjautuu monivuotiseen kehitys- ja tutkimushankkeeseen, jossa tutkija ja työyhteisö ovat tehneet tiivistä yhteistyötä. Kirjassa kuvataan sekä nuorisotyön opetussuunnitelman sisältö että suunnitelman syntyyn johtanut prosessi. Siinä annetaan malli, miten työyhteisö voi itse kehittää toimintaansa. Miksi nuorisotyötä tehdään? rakentaa teoriaa nuorisotyöstä työntekijävetoisesti. Tässä se tekee uuden avauksen Suomessa. Kirjassa puheenvuoroja saavat nuorisotyöntekijät, tutkijat ja nuorisotyön johto. Kirja soveltuu kaikille nuorisotyöstä kiinnostuneille

The effects of digestate pyrolysis liquid on the thermophilic anaerobic digestion of sewage sludge — Perspective for a centralized biogas plant using thermal hydrolysis pretreatment

The use of pyrolysis process to valorize digestate from anaerobic digestion (AD) of municipal sewage sludge for biochar production was piloted in a central biogas plant. The pyrolysis also generates pyrolysis liquid with high organics and nutrient contents that currently has no value and requires treatment, which could potentially be done in AD. As the pyrolysis liquid may contain inhibitory compounds, we investigated the effects of adding the pyrolysis liquid on AD of sewage sludge and thermal hydrolysis pretreated sewage sludge (THSS) simulating the full-scale centralized biogas plant conditions. In batch assays, the pyrolysis liquid as such did not produce any methane, and the 1% and 5% (v/w) shares suppressed the methane production from THSS by 14–19%, while a smaller decrease in methane production was observed with sewage sludge. However, in the semi-continuous reactor experiments, pyrolysis liquid at a 1% (v/w) share was added in sewage sludge or THSS feed without affecting the methane yields or digestate characteristics. The laboratory results indicated that pyrolysis liquid can be treated in AD, while extrapolating the results to the centralized biogas plant indicated minor increase in the overall methane production and an increased potential for ammonium recovery.publishedVersionPeer reviewe

Hydrothermal carbonisation of mechanically dewatered digested sewage sludge—Energy and nutrient recovery in centralised biogas plant

This study aimed to assess the role of hydrothermal carbonisation (HTC) in digestate processing in centralised biogas plants receiving dewatered sludge from regional wastewater treatment plants and producing biomethane and fertilisers. Chemically conditioned and mechanically dewatered sludge was used as such (total solids (TS) 25%) or as diluted (15% TS) with reject water in 30 min or 120 min HTC treatments at 210 °C, 230 °C or 250 °C, and the produced slurry was filtered to produce hydrochars and filtrates. The different hydrochars contributed to 20–55% of the original mass, 72–88% of the TS, 74–87% of the energy content, 71–92% of the carbon, above 86% of phosphorous and 38–64% of the nitrogen present in the original digestates. The hydrochars’ energy content (higher heating values were 11.3–12.2 MJ/kg-TS) were similar to that of the digestates, while the ash contents increased (from 43% up to 57%). HTC treatments produced filtrates in volumes of 42–76% of the dewatered digestate, having a soluble chemical oxygen demand (SCOD) of 28–44 g/L, of which volatile fatty acids (VFAs) contributed 10–34%, and methane potentials of 182–206 mL-CH4/g-SCOD without any major indication of inhibition. All 32 pharmaceuticals detected in the digestates were below the detection limit in hydrochars and filtrates, save for ibuprofen and benzotriazole in filtrate, while heavy metals were concentrated in the hydrochars but below the national limits for fertiliser use, save for mercury. The integration of HTC to a centralised biogas plant was extrapolated to enhance the annual biogas production by 5% and ammonium recovery by 25%, and the hydrochar was estimated to produce 83 GJ upon combustion or to direct 350 t phosphorous to agriculture annually.publishedVersionPeer reviewe

Ravinnevisio : Selvitys Pirkanmaan puhdistamolietteiden ja biojätteiden ravinteista ja niiden potentiaalisesta käytöstä

Selvityksen Pirkanmaan puhdistamolietteiden ja biojätteiden ravinteista ja niiden potentiaalisesta käytöstä on teettänyt Pirkanmaan ELY-keskus, Pirkanmaan Jätehuolto Oy, Tampereen Seudun Keskuspuhdistamo Oy ja Nokian Vesi Oy. Työn on toteuttanut Tampereen teknillinen yliopisto ja Luonnonvarakeskus. Työssä selvitettiin Pirkanmaan alueen ja erityisesti Tampereen seudun yhdyskuntajätevesien käsittelyssä muodostuvien puhdistamolietteiden ja biojätteiden ravinnesisältöä, käsittelyä biokaasulaitoksessa ja mädätysjäännöksen prosessointiin soveltuvia tekniikoita. Lisäksi selvitettiin mädätysjäännöksen tai siitä prosessoitujen lannoitevalmisteiden käyttöä maa- ja metsätaloudessa sekä viherrakentamisessa. Työn pidemmän aikavälin tavoitteena on yhdyskuntajäteveden puhdistamolietteiden ja biojätteiden sekä niiden sisältämien ravinteiden hyötykäytön edistäminen maakunnassa. Selvityksen perusteella Tampereen seudulla näyttäisi olevan puhdistamoliete- ja biojäteperäisten lannoitevalmisteiden ja maanparannusaineiden käyttöön soveltuvaa peltoalaa kohtuullisella kuljetusetäisyydellä. Tuotteiden laajamittainen hyötykäyttö ja ravinteiden kierrätys riippuu oleellisesti tuotteen myyntiketjun ja levityspalvelujen sekä tuotteen ominaisuuksien kehittämisestä, ohjaavien toimien ja lainsäädännön ohella. Nykyisen tietämyksen valossa suurin este puhdistamolietteiden hyödyntämiselle ovat ennakkoasenteet, sillä tehtyjen riskinarviointien perusteella puhdistamoliete- tai biojäteperäisten lannoitevalmisteiden käytöstä ei aiheudu vaaraa ihmisille