Resistance to forced airflow through layers of composting organic material

Abstract

The objective of this study was to adjust equations to estimate the static pressure gradient of airflow through layers of organic residues submitted to two stages of biochemical degradation, and to evaluate the static pressure drop of airflow thought the material layer. Measurements of static pressure drop in the layers of sugarcane bagasse and coffee husks mixed with poultry litter on day 0 and after 30 days of composting were performed using a prototype with specific airflow rates ranging from 0.02 to 0.13 m(3) s(-1) m(-2). Static pressure gradient and specific airflow rate data were properly fit to the Shedd, Hukill & Ives and Ergun models, which may be used to predict the static pressure gradient of air to be blown through the organic residue layers. However, the Shedd model was that which best represented the phenomenon studied. The static pressure drop of airflow increased as a power of the material layer thickness and showed tendency for decreasing with the biochemical degradation time of the organic material.

Improving green waste composting by addition of sugarcane bagasse and exhausted grape marc

“…Compost temperature is an indicator of microbial activity during composting, and a return to near ambient temperatures is a good indicator of the end of the bio-oxidative phase (Teixeira et al, 2015). The pattern of temperature changes through time was similar in all treatments (Table 3).…”

“…SCB was previously reported to improve the particle-size distribution during composting (Teixeira et al, 2015) and the particlesize distribution of the final product (Bustamante et al, 2011;Curtin and Mullen, 2007). Furthermore, SCB and EGM both extended the thermophilic period, which could lead to a more complete degradation of the GW (Section 3.1) and thus to an improved physical structure (especially the particle-size distribution) of the final compost.…”

“…The effects of SCB and EGM on temperature may also be explained by their enhancement of microbial numbers and activities, which could enhance the production of metabolic heat (Section 3.6). Furthermore, the high absorption capacity of these additives tends to limit evaporation and to therefore limit the heat losses associated with evaporation (Bustamante et al, 2013;Teixeira et al, 2015).…”

“…Mesopores in particular are commonly associated with the ability of substrates to retain water (Haynes and Belyaeva, 2009). Mohee et al (2015) and Teixeira et al (2015) both suggested that the high proportion of mesopores in SCB might contribute to a high WHC in the final compost product. In addition, the treatments with both SCB and EGM significantly reduced the CI value (Section 3.3), and Abad et al (2005) reported that WHC significantly increased with a decrease in CI value.…”

“…In the composting of organic waste from livestock, SCB is commonly used as the structuring agent, whose main purpose is to correct the water content of the mixture by forming porous spaces in the composting mass. This increases the availability of oxygen and reduces the loss of static pressure in systems using forced aeration (Teixeira et al, 2015). The addition of sufficient SCB, which is acidic, can also enhance the nutrient transformation of organic wastes by controlling the pH (Cole et al, 2016).…”