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Utilizing stable carbon isotope data to account for aceticlastic and non-aceticlastic pathways of methane generation, a model was created to describe laboratory batch anaerobic decomposition of cellulosic materials (office paper and cardboard). The total organic and inorganic carbon concentrations, methane production volume, and methane and CO(2) partial pressure values were used for the model calibration and validation. According to the fluorescent in situ hybridization observations, three groups of methanogens including strictly hydrogenotrophic methanogens, strictly aceticlastic methanogens (Methanosaeta sp.) and Methanosarcina sp., consuming both acetate and H(2)/H(2)CO(3) as well as acetate-oxidizing syntrophs, were considered. It was shown that temporary inhibition of aceticlastic methanogens by non-ionized volatile fatty acids or acidic pH was responsible for two-step methane production from office paper at 35 degrees C where during the first and second steps methane was generated mostly from H(2)/H(2)CO(3) and acetate, respectively. Water saturated and unsaturated cases were tested. According to the model, at the intermediate moisture (150%), much lower methane production occurred because of full-time inhibition of aceticlastic methanogens. At the lowest moisture, methane production was very low because most likely hydrolysis was seriously inhibited. Simulations showed that during cardboard and office paper biodegradation at 55 degrees C, non-aceticlastic syntrophic oxidation by acetate-oxidizing syntrophs and hydrogenotrophic methanogens were the dominant methanogenic pathways.

The presence of paper in municipal solid waste (MSW) interferes with the efficiency of composting plants. The compost feedstock to these plants is between 12% and 27% paper on a dry weight basis, with an initial C:N ratio ranging from 32:1 to 57:1. Tests of the last aerobic biodegradability (LAB) of the type of paper present in paper and cardboard packaging were carried out, following UNE-EN 14046 standards. The results obtained, measured through the quantity of CO(2) generated over 45 days, compared with the maximum that could be produced (ThCO(2)), showed that the presence of paper retards, to a great degree, the biodegradation of organic material in general. Specifically, the presence of papers with a degradation D (%) >60% at 45 days (white (W) and recycled paper (R)) could be allowed, but always in proportions that did not exceed 27% in dry weight. These results can be achieved with an industrial level process, pre-treated by trituration.

In recent years thermal utilization of mixed wastes and solid recovered fuels has become of increasing importance in European waste management. Since wastes or solid recovered fuels are generally composed of fossil and biogenic materials, only part of the CO(2) emissions is accounted for in greenhouse gas inventories or emission trading schemes. A promising approach for determining this fraction is the so-called radiocarbon method. It is based on different ratios of the carbon isotopes (14)C and (12)C in fossil and biogenic fuels. Fossil fuels have zero radiocarbon, whereas biogenic materials are enriched in (14)C and reflect the (14)CO(2) abundance of the ambient atmosphere. Due to nuclear weapons tests in the past century, the radiocarbon content in the atmosphere has not been constant, which has resulted in a varying (14)C content of biogenic matter, depending on the period of growth. In the present paper (14)C contents of different biogenic waste fractions (e.g., kitchen waste, paper, wood), as well as mixtures of different wastes (household, bulky waste, and commercial waste), and solid recovered fuels are determined. The calculated (14)C content of the materials investigated ranges between 98 and 135pMC.