Anaerobic Digestion of Solid Residues on the Bolivian Altiplano

Rene Alvarez

Research output: ThesisDoctoral Thesis (compilation)

Abstract

Anaerobic digestion and the production of biogas can provide an efficient means of meeting energy needs locally and reducing organic loading due to untreated waste material in water recipients. Furthermore, residues after anaerobic digestion may be used as a fertilizer to improve the soil in many parts of the world. Most natural organic waste can be used in anaerobic digestion. In developing countries, the primary substrate is cattle dung, but agricultural residues and aquatic flora may be added to co-digestion processes to produce more gas. Waste generated in urban areas (the organic fraction of municipal waste and industrial waste) are in principle also amenable to anaerobic digestion. However, these feedstocks have not been thoroughly explored in developing countries. Furthermore, harsh environmental conditions in some regions may limit the application of anaerobic digestion technology.

The objective of the current work was to experimentally investigate anaerobic digestion of organic residues with specific emphasis on conditions particular to the Bolivian Altiplano. There are several potential barriers to the successful implementation of biogas production on the Altiplano. The aspects to which most attention was devoted here were the low mean temperature, the large daily temperature fluctuations and the character of the raw material typical for the region.

Experiments conducted on semi-continuous anaerobic digestion from llama and cow manure showed that temperature, the hydraulic retention time (HRT), and the manure content in the feed were the significant factors, in this order, whereas the effect of pressure was not significant in the range studied. Llama manure appears to be the best raw material from the Altiplano, because of its high volatile solids content, high nutrient content and availability. In general, the methane yields obtained were lower than reported value at sea level, and this was attributed to the quality of the volatile solids (VS) in the manure, probably a consequence of the feed source of the livestock and the harsh environmental conditions at high altitude. The biogas productivity and methane yield (0.008 and 0.011 m3 biogas kg-1 dung, 0.03 and 0.01 m3 CH4 kg-1VS added, for cow and llama manure, respectively) obtained at 11oC, and a hydraulic residence time (HRT) of 50 days, could be increased up to 0.035-0.133 m3 biogas kg-1 mixture of substrate (0.09-0.15 m3 CH4 kg-1 VS added) by increasing the temperature and co-digestion with agricultural residues or aquatic flora.

The anaerobic digestion of llama, cow and sheep manure in a semi-continuous process subject to a square-wave daily temperature fluctuation was also studied. The pH (7.2) in the effluent and the average methane content of the biogas (55-56%) were stable indicating a well-balanced biomethanation process. Furthermore, the mean biogas productivity was higher than that obtained at the average temperature.

A semi-continuous co-digestion process treating solid slaughterhouse waste (rumen, stomach content and blood from cattle and swine), fruit &vegetable waste, together with manure (from cattle and swine) in a mesophilic process showed expected results, such as a reduction of volatile solid contents of between 50 and 65%, and methane yield of about 0.3 m3 CH4 kg-1 VS added, at organic loading rates up to 1.3 kg VS m-3d-1. These results show that anaerobic digestion offers a potential means of decreasing the environmental burden, and at the same time providing biogas for local energy needs.

The domestic energy needs of the rural population of the Altiplano can be met if the animal dung is used for biogas production in small-scale biogas digesters. However, the harsh environment conditions demand systems or means of increasing the average temperature in the digesters.
Original languageEnglish
QualificationDoctor
Awarding Institution
  • Department of Chemical Engineering
Supervisors/Advisors
  • Lidén, Gunnar, Supervisor
Award date2006 Nov 16
Publisher
Print ISBNs91-7422-128-0
Publication statusPublished - 2006

Bibliographical note

Defence details

Date: 2006-11-16
Time: 10:30
Place: Lecture hall C, at the Center for Chemistry and Chemical Engineering, Getingevägen 60, Lund.

External reviewer(s)

Name: Rintala, Jukka
Title: Professor
Affiliation: Department of Biological and Environmental Sciences, University of Jyväakylä, Finland

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Subject classification (UKÄ)

  • Chemical Engineering

Keywords

  • Bioteknik
  • Biotechnology
  • Altiplano
  • renewable energy
  • temperature fluctuation
  • low temperature
  • farm-scale digestion
  • manure
  • solid residues
  • Anaerobic Digestion
  • biogas

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