The use of respiration indices in the composting process: a review

Abstract

Respiration is directly related to the metabolic activity of a microbial population. Micro-organisms respire at higher rates in the presence of large amounts of bioavailable organic matter while respiration rate is slower if this type of material is scarce. In the composting process respiration activity has become an important parameter for the determination of the stability of compost. It is also used for the monitoring of the composting process and it is considered an important factor for the estimation of the maturity of the material. A wide range of respirometric protocols has been reported based either on CO2 production, O2 uptake or release of heat. The most common methods are those based on O2 uptake. Respirometric assays are affected by a number of parameters including temperature, humidity, and both incubation and pre-incubation conditions. Results from respirometries are generally expressed as ‘respiration indices’, most of them with their own units and basis. In consequence, some confusion exists when referring and comparing respiration indices. This is particularly important because current and future legislations define and measure the biological stability of waste on the basis of respiration activity of the material. This paper discusses and compares most common respiration indices currently used.

Assessment of Microbial Communities and Their Relationship with Enzymatic Activity during Composting

“…As shown in Figure 2, temperature increased after 2 days and stayed above 55˚C for more than 6 days, another peak was observed after 10 days and then it started to drop gradually and reached ambient temperature after three weeks. Respiration rate is higher in the presence of large amounts of bioavailable organic matter for microorganisms while it is slower if this type of material is scarce [14]. OUR followed the same pattern as temperature.…”

Augmenting Composting Microbial Community with Thermophilic Cellulolytic Organisms for Enhanced Degradation of Phenolic Compounds in Creosote Treated Wood Waste

“…Wong et al [3] reported that the CO 2 evolution rate rapidly declined from 7.33 to 3.23 mg CO 2 /g VS/d and 5.51 to 3.38 mg CO 2 /g VS/d in 3 weeks and gradually declined to 2.43 mg CO 2 /g VS/d and 1.89 CO 2 /g VS/d after 7 weeks of in-vessel composting of high sludge (1 sludge: 1.5 horse stable straw bedding waste) and low sludge (1 sludge: 2.9 horse stable straw bedding waste), respectively. The final products for control and inoculated experiment had a threshold of under 8 mg CO 2 -C per g carbon per day and are considered stable according to Gomez and Lima [50]. Rekha et al [51] reported 49% and 95% increase in GI values in sediment from upper and lower stratus after 14 weeks of composting of contaminated lake sediments.…”

Evaluation of Biological Activity of Cellulose Pulp by Means of the Static Respiration Index (At₄)/ Ocena Aktywności Biologicznej Pulpy Celulozowej Testem Respiracyjnym At₄

“…SOUR) [1,3]. Table 1 presents selected tests conducted under aerobic conditions [4]. At present, the respiration indices are regarded as the basic parameters which serve the purpose of assessment of the compost stability, including its quality.…”

“…AT 4 is a parameter that determines the demand for oxygen necessary for the decomposition of waste within four days. Table 2 presents the value of AT 4 for the selected components of municipal waste [3]. Not only does the AT 4 index depict the loss of the total mass organic matter as a result of mineralisation processes, but also a decrease in the capacity of the organic matter to further decompose in the aerobic process.…”

“…3 Selected cellulose pulp (P) samples inoculated with compost (K) AT 4 , humidity, total nitrogen, total phosphorus, losses on ignition and TOC were determined in the studied waste. Upon determination of the primary moisture at the stage of sample preparation, before the analysis itself, the sample was moistened accordingly.…”