Anaerobic Digestion in Sustainable Biomass Chains

262 Pages·2009·3.81 MB·English

Anaerobic Digestion in
Sustainable Biomass Chains

Claudia Patricia Pabón Pereira
THESIS COMMITTEE

THESIS SUPERVISORS:

PROF. DR IR R. RABBINGE
UNIVERSITY PROFESSOR, SUSTAINABLE DEVELOPMENT AND FOOD SECURITY
WAGENINGEN UNIVERSITY

PROF. DR IR J.B. VAN LIER
PROFESSOR OF ANAEROBIC WASTEWATER TREATMENT FOR REUSE AND IRRIGATION,
WAGENINGEN UNIVERSITY

THESIS CO-SUPERVISORS:

DR IR M.A. SLINGERLAND
ASSISTANT PROFESSOR, PLANT PRODUCTION SYSTEMS GROUP,
WAGENINGEN UNIVERSITY

OTHER MEMBERS:
PROF. DR. IR L.O. FRESCO, UNIVERSITY OF AMSTERDAM
DR E. GIRALDO, AMERICAN WATER, VOORHEES, USA
PROF. DR J.P.M. SANDERS, WAGENINGEN UNIVERSITY
PROF. DR.IR A.J.M. STAMS, WAGENINGEN UNIVERSITY

This research was conducted under the auspices of the Graduate School of SENSE (Socio-
Economic and Natural Sciences of the Environment) and PE&RC (Production Ecology &
Resource Conservation).
Anaerobic Digestion in
Sustainable Biomass Chains

Claudia Patricia Pabón Pereira

Thesis
Submitted in partial fulfillment of the requirements for the degree of doctor
at Wageningen University
by the authority of the Rector Magnificus
Prof. Dr. M.J. Kropff,
in the presence of the
Thesis Committee appointed by the Doctorate Board
to be defended in public
on Tuesday 30 June 2009
at 11 am in the Aula
Claudia Patricia Pabón Pereira
Anaerobic Digestion in Sustainable Biomass Chains
Pages: 262
Ph.D. Thesis, Wageningen University, Wageningen, NL (2009)
With references – With summaries in English and Dutch

ISBN: 978-90-8585-432-6
A todos los seres con quienes comparto
el increible misterio de vivir,
unidos desde el corazón

Contents

Abstract 9

1. General Introduction 11

2. A sustainability framework for analyzing the role of anaerobic digestion
in biomass cascades 33

3. Optimizing an OxiTop® protocol for screening plant material suitable
for anaerobic digestion 49

4. Identifying valuable plant material for sustainable energy production by
determination of its anaerobic biodegradability 71

5. Impact of crop-manure ratios and digestion time on the fertilizing characteristics
of liquid and solid digestate during codigestion 99

6. Sensitivity analysis on the net energy contribution of anaerobic digestion
to biomass cascades 113

7. The added value of anaerobic digestion to cassava bioethanol production
in Colombia: Energy, GHG, water and land implications 135

8. Unfolding possibilities for anaerobic digestion as part of biomass cascades in
Colombia 169

9. Summary and General Discussion 205

References 229

Appendixes 245

Abstract

This thesis evaluates the potential contribution of anaerobic digestion (AD) to the sustainability
of biomass chains. Results provide insights in the technological potential to recover energy and
valuable by-products from energy crops and residues, and evaluate biomass cascades involving
AD technology for their feasibility and desirability. Embedding AD in biomass chains
addresses current constraints towards increased use of biomass for energy production
considering land competition and environmental pollution. In this context, so far the major
advantages of AD to improve energy efficiency and closing material cycles have received, thus
far, limited attention. As part of the experimental research an Oxitop® protocol was refined for
screening plant material suitable for anaerobic digestion based on their energy content.
Environmental factors influencing the test outcome are the use of NaOH pellets for CO
2
scavenging, substrate pretreatment, microbial culture, and type of buffer. The use of NaOH
pellets and substrate pretreatments were most influential on the results. By means of the
developed Oxitop® protocol the relationship between plant ligno-cellulosic composition and
the Biochemical Methane Potential (BMP) and first-order hydrolysis constant (k ) was
h
researched. The Acid Detergent Fibre (ADF) and the Neutral Detergent Fibre (NDF) as
analyzed by the van Soest method were proposed as suitable plant characterization techniques
for predicting BMP and k , respectively. The model proposed was further used to predict the
h
biodegradability of 114 European plant samples identifying interesting crops and crop residues
suitable for anaerobic digestion. Batch experiments on digestate quality during codigestion of
maize silage and manure showed an increase of 20-26% and 0-36% in solublised NH + and
4
PO 3-, respectively, after 2 months of digestion. The largest fraction of the inorganic nutrients
4
was found in the liquid fraction of the digestate, i.e. 80-92% NH + and 65-74% PO 3-. Increase
4 4
in manure content in the mixture showed a positive effect in the methane production rate.
Digestion time and increased proportion of maize silage in the mixture positively influenced
the availability of PO 3-. The added value of AD within different biomass cascades was
4
evaluated by means of a sustainability framework developed for the purpose. The sensitivity
analysis of the energy balance of an AD facility showed that the most important energy loss
when a high value substrate such as energy maize is employed are heat losses induced by
restricted reuse possibilities within the cascade. In contrast, when low energy substrates such as
manure are used, indirect energy inputs embedded in infrastructure become significant. The
developed sustainability framework was applied for the Colombian case. Results show that
production of bio-ethanol from cassava is only sustainable from an energy and greenhouse gas
(GHG) perspective when energy recovery from the process residues, using AD, is part of the
process. The exact outcome of the evaluation largely depends on variables like substrate
drying, type of fuel used, reuse possibilities for the digestate and type of applied AD system.
During the study of other Colombian biofuel cascades the contribution of by-products was
shown to be crucial, constituting 41-68% of the sum of all energy flows. For oil palm,
sugarcane, panelacane and cassava, the estimated energy contribution of the by-products to the
different biofuel systems fluctuate between 51-158, 122-290, 71-170, and 36-71 GJ.ha-1yr-1,
respectively. AD had also a positive impact on nutrient recovery and water savings in the
studied chains. The energy, nutrient and water benefits were set in perspective by giving an
indication on the economic benefits and land savings potentially attainable under Colombian
conditions.