Endre søk
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
When and why is pre-treatment of substrates for anaerobic digestion useful?
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
2015 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Anaerobic digestion (AD) plays a key role in the recovery of renewable energy, in the form of biogas, and nutrients from waste materials. Pre-treatment of AD substrates has the potential to improve process performance in terms of increased methane yield and solids reduction, but pretreatments are not yet widely implemented into full-scale AD systems. The aims of this thesis were to identify conditions that determine when pre-treatment has a positive impact on an AD system and ways to improve the practical utility of pre-treatment impact assessment. Key steps towards meeting these aims were to determine and critically analyse effects of pre-treatments on AD, and current evaluation schemes at three levels: AD substrate level – Direct effects on the substrate’s chemical and physical characteristics and its biodegradability/bioavailability; Local AD system level – Effects of pre-treatment on the AD process and its outputs, required inputs and (local) upstream and downstream processes. System boundaries are “at the gate” of the AD plant and the system analysis may consider energy and/or financial parameters; Expanded AD System level – Includes indirect effects of pre-treatment, with system boundaries including external processes. The system analysis may address environmental and/or economic effects. Different substrate traits represent different types and degrees of limitations to optimal AD performance that can be met by different pre-treatment mechanisms. Most importantly, potential mechanical problems must be handled by dilution and/or homogenisation and unwanted components, as generally found in source-sorted food waste from households (FW), must be separated. These traits may hinder the actual operation of AD and the potential for recovery of nutrients, which is often the motivation for biological waste treatment. When these practical barriers are overcome, pre-treatment focus may be directed towards maximizing the conversion of organic material to biogas, which is potentially limited by the rate and/or extent of hydrolysis. Lignocellulosic structures and aerobically stabilised biological sludge represent significant barriers to hydrolysis, which can be overcome by pre-treatment-induced solubilisation. Other particulates are merely hydrolysis-limited by their size, which can be reduced by specific pre-treatments. Finally, substrates may contain non-biodegradable organic compounds, which need to be chemically transformed in order to be converted to biogas. The substrates considered for AD incorporate these traits in varying degrees and even among substrates of the same category, such as plant material and excess sludge from wastewater treatment (WWT), the potential effect of pretreatments may vary considerably. Overcoming the substrate barriers via pre-treatment may potentially improve the AD system by enhancing operational stability, increasing methane yields and solids reduction under similar operating conditions to those without pre-treatment or by increasing methane productivity by allowing reductions in hydraulic retention time without changing the methane yield. However, the required inputs as well as the associated effects on related sub-processes must also be considered. The ultimate usefulness of a pre-treatment in a specific system is determined by the mass- and energy balance and the associated financial or environmental costs/values of inputs and outputs. The accuracy and applicability of pre-treatment impact assessment is challenged by method limitations and lack of transparency. A common measure of the pre-treatment effects is COD solubilisation, but the interpretation is complicated by the application of different measurementapproaches. In addition, solubilisation of COD as a result of pre-treatment does not necessarily translate into increases in operational methane yields. This is due to potential formation of refractory compounds and the fact that hydrolysis is not necessarily rate limiting for all particulates. Pre-treatments’ effects on biodegradability and degradation rates can be better assessed by BMP tests (biochemical methane potential), provided that the test conditions are appropriate and the tests’ limitations are properly considered. However, extrapolation of BMP results to continuous processes is complicated by the batch mode of the tests. On the other hand, results from continuous trials allow assessments of methane yields in practical systems and the digestate’s physico-chemical properties, but are inevitably tied to the specific process conditions tested. Thus, results from multiple experimental conditions, possibly strengthened by computer simulations, are necessary for generalisations of pre-treatment effects on AD process performance. Pre-treatments have the potential to considerably improve AD systems, but their implementation must to be guided by the actual improvement potential of the specific substrate and valued in theirspecific context with respect to process design and framework conditions.

sted, utgiver, år, opplag, sider
Luleå tekniska universitet, 2015.
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
HSV kategori
Forskningsprogram
Avfallsteknik
Identifikatorer
URN: urn:nbn:se:ltu:diva-17712Lokal ID: 4cb25c0a-a2a0-428f-83ea-c076c5cb7c33ISBN: 978-91-7583-376-7 (tryckt)ISBN: 978-91-7583-377-4 (digital)OAI: oai:DiVA.org:ltu-17712DiVA, id: diva2:990717
Disputas
2015-09-22, F1031, Luleå tekniska universitet, Luleå, 10:00
Opponent
Tilgjengelig fra: 2016-09-29 Laget: 2016-09-29 Sist oppdatert: 2023-11-29bibliografisk kontrollert

Open Access i DiVA

fulltekst(5029 kB)4744 nedlastinger
Filinformasjon
Fil FULLTEXT01.pdfFilstørrelse 5029 kBChecksum SHA-512
58f24a4dbbebc4a4d6e704c6608b2b7f7fd0d7df4c0236e0aa0177bb410ea27593856cac9fc90910f92f3b8e72c23525e7c36ccb749d1c303a362969622d4352
Type fulltextMimetype application/pdf

Person

Carlsson, My

Søk i DiVA

Av forfatter/redaktør
Carlsson, My
Av organisasjonen

Søk utenfor DiVA

GoogleGoogle Scholar
Totalt: 4747 nedlastinger
Antall nedlastinger er summen av alle nedlastinger av alle fulltekster. Det kan for eksempel være tidligere versjoner som er ikke lenger tilgjengelige

isbn
urn-nbn

Altmetric

isbn
urn-nbn
Totalt: 694 treff
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf