A Fractal-like Kinetics Equation to Calculate Methane Landfill Production

MERAZ, R.L.; VIDALES, A M; DOMINGUEZ, A.

FUEL

Elsevier

Año: 2004 vol. 83 p. 73 - 80

0016-2361

Landfill appears as a convenient choice to get rid of municipal solid waste while providing energy, due to methane generated through anaerobic fermentation. However, without capture and treatment landfill gas is considered an important source of atmospheric methane. The control and use of this gas require knowledge of both, current yield and long-term accumulative production. These values are usually calculated with mathematical expressions that consider 100% of conversion, and homogeneous chemical reactivity inside the fill. Nevertheless, fermentation in landfills is erratic and spatially heterogeneous. This work introduces a fractal-like chemical kinetics equation to calculate methane generation rate from landfill, QCH4QCH4 (m3/year), in the way: QCH4 ¼ L03/year), in the way: QCH4 ¼ L0 P j P i MijC0MijC0 ijkiðtjÞ2ds =2 exp½2kitj; where fermentable wastes are partitioned in readily, moderately and slowly biodegradable categories, L0 is the potential of methane yield of refuse (m3/tonne under standard conditions), ds is the solid-phase fracton dimension, ki is the reaction kinetics constant of waste category i (year21), and tj is the time from the year of burying j (year), C0kiðtjÞ2ds =2 exp½2kitj; where fermentable wastes are partitioned in readily, moderately and slowly biodegradable categories, L0 is the potential of methane yield of refuse (m3/tonne under standard conditions), ds is the solid-phase fracton dimension, ki is the reaction kinetics constant of waste category i (year21), and tj is the time from the year of burying j (year), C0L0 is the potential of methane yield of refuse (m3/tonne under standard conditions), ds is the solid-phase fracton dimension, ki is the reaction kinetics constant of waste category i (year21), and tj is the time from the year of burying j (year), C0ds is the solid-phase fracton dimension, ki is the reaction kinetics constant of waste category i (year21), and tj is the time from the year of burying j (year), C0j (year), C0 ij (kg/tonne) and Mij (kg) are the initial concentration and the mass of waste category i landfilled in year j, respectively. The idea behind this equation is that methane production kinetics is limited by the diffusion of hydrolyzed substrate into a heterogeneous solid-phase towards discrete areas, where methanogenesis occurs. A virtual study for a hypothetical case is developed. The predictions from this fractal approach are contrasted with those coming from two equations broadly used in the industrial work. The fractal-like kinetics equation represents better the heterogeneous nature of the fermentation in landfills.(kg/tonne) and Mij (kg) are the initial concentration and the mass of waste category i landfilled in year j, respectively. The idea behind this equation is that methane production kinetics is limited by the diffusion of hydrolyzed substrate into a heterogeneous solid-phase towards discrete areas, where methanogenesis occurs. A virtual study for a hypothetical case is developed. The predictions from this fractal approach are contrasted with those coming from two equations broadly used in the industrial work. The fractal-like kinetics equation represents better the heterogeneous nature of the fermentation in landfills.j, respectively. The idea behind this equation is that methane production kinetics is limited by the diffusion of hydrolyzed substrate into a heterogeneous solid-phase towards discrete areas, where methanogenesis occurs. A virtual study for a hypothetical case is developed. The predictions from this fractal approach are contrasted with those coming from two equations broadly used in the industrial work. The fractal-like kinetics equation represents better the heterogeneous nature of the fermentation in landfills.