%0 Journal Article
%T Phytotoxicity Evolution of Biowastes Undergoing Aerobic Decomposition
%A M. R. Soares
%A C. Matsinhe
%A S. Belo
%A M. J. Quina
%A R. Quinta-Ferreira
%J Journal of Waste Management
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/479126
%X This study is mainly focused on the phytotoxicity improvement within five to six weeks of thermophilic composting of biowastes. Two sets of experiments were conducted involving both sawdust and rice husk as bulking agents, which were composted in self-heating reactors with potato-peel industrial waste and grass clippings as organic materials. The main variables observed over time were temperature, oxygen uptake rate (OUR), biodegradability, and germination index (GI). The effects of compost water extracts on seed germination and primary root growth of garden cress (Lepidium sativum) were measured to calculate the germination index (GI). The biodegradability was well assessed by measuring lignin content, using the Klason method. The experimental results showed that initial compositions strongly determined the profiles of phytotoxicity and the period of maturation. The phytotoxicity assessment in the experiments with sawdust revealed that after 39 days of composting, the GI attained the maximum value of 30%, but using rice husk, it was possible to reach 70% in the same period of time. Our findings showed that, at a certain point, higher cumulative OUR led to lower germination index, and proportional relationship between the cumulative OUR and GI was observed, after thermophilic phase. 1. Introduction Nowadays, the natural resources are consumed at unsustainable rates, and consequently a huge amount of waste is produced, which can cause environmental damage if it is not well managed. In particular, the European Union policy states that the diversion of biowastes from landfill to anaerobic digestion or to composting should be improved for reducing pollution and recovering energy or soil conditioner materials. Composting can be defined as the aerobic microbial decomposition of organic matter, under controlled conditions that allow the development of thermophilic temperatures as a result of the heat released in the biochemical reactions, leading to a stabilized and sanitized final product (free of pathogens and seeds), commonly known as compost [1]. Indeed, although composting is not a recent technology, it can be considered as one of the most flexible methods for handling biodegradable wastes, from small scales such as household bins to large industrial plants [2]. To successfully accomplish composting, favorable physical and chemical conditions to the growth and activity of microorganisms should be promoted, accounting for some essential nutrients, namely, carbon and nitrogen as well as oxygen for metabolic activity. In this context, it is important to
%U http://www.hindawi.com/journals/jwm/2013/479126/