René Alvarez

Lund University, Lund, Skane, Sweden

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Publications (5)7.24 Total impact

  • René Alvarez, Gunnar Lidén
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    ABSTRACT: Biogas production in anaerobic digestion in farm-scale units is typically performed under mesophilic conditions when used for producing domestic fuel and stabilizing animal waste for the use of digested manure as a fertilizer. Previous studies on the digestion of llama and cow manure have shown the feasibility of producing biogas under altiplano conditions (low pressure and low temperature) and of llama manure as a promising feedstock. The present study concerns the utilization of various mixtures of feedstocks from the Bolivian altiplano under low temperature conditions (18–25 °C). Laboratory scale experiments were performed on the digestion of mixtures of llama, sheep and cow manure in a semi-continuous process using ten 2-L stainless steel digesters to determine the effects of organic loading rate (OLR) and the feed composition. The semi-continuous operation of mixture of llama–cow–sheep manure proved to be a reliable system, which could be operated with good stability. The results suggest that in a system digesting a mixture of llama-cow-sheep manure at low temperature (18–25 °C) the maximum OLR value is between 4 and 6 kg VS m3 d−1. The methane yields obtained in the mixture experiments were in the range 0.07–0.14 m3 kg−1 VS added, with a methane concentration in the gas of between 47 and 55%.
    Biomass and Bioenergy. 01/2009;
  • René Alvarez, Gunnar Lidén
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    ABSTRACT: The aim of the current study was to examine effects of daily temperature variations on the performance of anaerobic digestion. Forced square-wave temperature variations (between 11 and 25, 15 and 28, and 19 and 32 degrees C) were imposed on a bench-scale digester using a mixture of llama-cow-sheep manure in a semi-continuous process. The volumetric biogas production rate, methane yield, and the volatile solid reductions were compared with the results obtained from anaerobic digestion (AD) at constant temperatures. The forced cyclic variations of temperature caused large cyclic variations in the rate of gas production and the methane content. As much as 94-97% of the daily biogas was obtained in the 12h half-cycle at high temperature. The values for volumetric biogas production rate and methane yield increased at higher temperatures. The average volumetric biogas production rate for cyclic operation between 11 and 25 degrees C was 0.22Ld(-1)L(-1) with a yield of 0.07m3CH4kg(-1) VS added (VSadd), whereas for operation between 15 and 29 degrees C the volumetric biogas production rate increased by 25% (to 0.27Ld(-1)L(-1) with a yield of 0.08m3CH4kg(-1) VSadd). In the highest temperature region a further increase of 7% in biogas production was found and the methane yield was 0.089m(3)CH(4)kg(-1) VSadd. The employed digester showed an immediate response when the temperature was elevated, which indicates a well-maintained metabolic capacity of the methanogenic bacteria during the period of low temperature. Overall, periodic temperature variations appear to give less decrease in process performance than a priori anticipated.
    Bioresource Technology 11/2008; 99(15):7278-84. · 4.75 Impact Factor
  • René Alvarez, Gunnar Lidén
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    ABSTRACT: Quinoa stalk (Chenopodium quinoa Willd.) from agricultural crop residue, totora (Schoenoplectus tatora) and o-macrophytes (aquatic flora) from Lake Titicaca (on the Bolivian Altiplano) were studied in a wet anaerobic co-digestion process together with manure from llama, cow and sheep. Anaerobic semi-continuous experiments were performed in (10) 2-l reactors at a temperature of 25 degrees C with 30 days of hydraulic retention time (HRT) and an organic loading rate (OLR) of 1.8 kg VS m(-3) d(-1). Totora was found to be the best co-substrate. In mixture ratios of 1:1 (VS basis), it increased the biogas productivity by 130% for llama manure, 60% for cow manure, and 40% for sheep manure. It was possible to use up to 58% (VS basis) of totora in the substrate. Higher concentrations (including pure totora) could not be digested, as that caused acidification problems similar to those caused by other lignocellulosic materials. When quinoa and o-macrophytes were used as co-substrates, the increase in biogas productivity was slightly less. However, these co-substrates did not cause any operational problems. An additional advantage of quinoa and o-macrophytes was that they could be used in any proportion (even in pure form) without causing any destabilization problems in the anaerobic digestion process.
    Waste Management 01/2008; 28(10):1933-40. · 2.49 Impact Factor
  • René Alvarez, Gunnar Lidén
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    ABSTRACT: The potential of semi-continuous mesophilic anaerobic digestion (AD) for the treatment of solid slaughterhouse waste, fruit-vegetable wastes, and manure in a co-digestion process has been experimentally evaluated. A study was made at laboratory scale using four 2L reactors working semi-continuously at 35°C. The effect of the organic loading rate (OLR) was initially examined (using equal proportion of the three components on a volatile solids, VS, basis). Anaerobic co-digestion with OLRs in the range 0.3–1.3kgVSm−3d−1 resulted in methane yields of 0.3m3kg−1VS added, with a methane content in the biogas of 54–56%. However, at a further increased loading, the biogas production decreased and there was a reduction in the methane yield indicating organic overload or insufficient buffering capacity in the digester.In the second part of the investigation, co-digestion was studied in a mixture experiment using 10 different feed compositions. The digestion of mixed substrates was in all cases better than that of the pure substrates, with the exception of the mixture of equal amounts of (VS/VS) solid cattle–swine slaughterhouse waste (SCSSW) with fruit and vegetable waste (FVW). For all other mixtures, the steady-state biogas production for the mixture was in the range 1.1–1.6Ld−1, with a methane content of 50–57% after 60 days of operation. The methane yields were in the range 0.27–0.35m3kg−1VS added and VS reductions of more than 50% and up to 67% were obtained.
    Renewable Energy. 01/2008; 33(4):726-734.
  • René Alvarez, Saul Villca, Gunnar Lidén
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    ABSTRACT: Methane production from llama and cow manures from the Bolivian high plateau (The “Altiplano”) was studied using a parallel reactor set-up consisting of 10 lab-scale biogasifiers. The effects of pressure (495 and 760mmHg), temperature (11 and 35∘C), hydraulic retention time (20 and 50 days), and manure content in the slurry (10%, 20% and 50%) were evaluated with respect to productivity and methane yields based on two 24-1 fractional factorial designs with 8 treatments for each kind of manure. The reactors were operated semi-continuously with daily manure feeding for periods between 50 and 100 days. Temperature was the main factor effect found, and the hydraulic retention time and the manure content in feed were also found significant whereas the effect of pressure was not significant in the range studied. The methane yield obtained with cow manure at 11∘C was between 6.4 and 33.6lCH4kg-1VS (volatile solids added) whereas at 35∘C the methane yield was between 49.6 and 131.3lCH4kg-1VS. The methane yield from llama manure was somewhat lower than for cow manure (between 3.3 and 19.3lCH4kg-1VS at 11∘C and between 35.6 and 84.1lCH4kg-1VS at 35∘C, respectively). However, overall llama manure was found to be the best raw material of the two for biogas production, due to its high content of volatile solid—higher than has been previously reported for most manures—and also its high nitrogen and phosphorous content.
    Biomass & Bioenergy - BIOMASS BIOENERG. 01/2006; 30(1):66-75.

Publication Stats

104 Citations
7.24 Total Impact Points

Institutions

  • 2008–2009
    • Lund University
      • Department of Chemical Engineering
      Lund, Skane, Sweden