The effect of sewage sludge biochar on peat-based growing media

Abstract

School of engineering, rMit university, Melbourne, australia; d Departamento de contaminación ambiental, instituto de ciencias agrarias, cSic, Madrid, Spain ABSTRACT Peat is the main component of growing media in horticulture. Increasing demand, environmental concerns and rising costs for peat make the search for alternative materials imperative. Much research has been performed aiming to find high quality and low cost substrates from different organic wastes such as compost and thus decrease peat consumption. Biochar is a carbon-rich material that has attracted important research as a soil amendment. However, its potential utilization as a peat substitute for growing media formulation remains less well explored. The aim of this study was to evaluate the effects of sewage sludge and sewage sludge biochar on peat properties as growing media and on lettuce (Lactuca sativa) growth. Sewage sludge transformation into biochar proved to be a sustainable waste management approach in order to promote their future use as growing media components. Addition of biochar from sewage sludge increased the N, P and K content of growing media. The biochar addition to peat at a 10%vol rate increased lettuce biomass production by 184-270% and the shoot length by 137-147% despite hydrophysical properties not being improved. Also, biochar addition had a positive effect on growing media microbial biomass which increased more than 966%. In spite of the higher metal concentration in biochar than in sewage sludge, their transfer to plants seems to be reduced when compared with direct sewage sludge use.

Hydrochars from Biosolids and Urban Wastes as Substitute Materials for Peat

“…The values of the hydrophysical properties are similar to those obtained by Méndez et al () for growing media prepared with peat and deinking sewage sludge biochar (pyrolysis temperature: 300 °C), using the same proportions than in the present study. Bulk density and air space were higher than the values obtained by Méndez et al () after mixing peat with sewage sludge biochar prepared at 450 °C.…”

“…In order to study the effect of hydrochar addition on peat properties, two hydrochar–peat mixtures were prepared by adding hydrochars (HSL or HUW) to peat (PT) at a 50% volume rate (PT + HSL and PT + HUW). This mixing ratio has been used in previous experiments where biochar has been used as a peat substitute (Méndez et al, , ). Samples were manually mixed with the help of a stainless steel spatula.…”

“…In general, the full replacement of peat in growing media is limited by the lower water holding capacity of the biochars (Méndez et al, ; Nieto et al, ). In spite of this, biochar–peat mixtures can present better properties for its use as growing media than peat, leading to an increase in plant biomass production, which has been verified for lettuce ( Lactuca sativa ) (Méndez et al, ; Méndez et al, ; Nieto et al, ) and Calathea rotundifolia (Tian et al, ). Finding adequate materials to achieve a full replacement of peat in growing media will require to improve the transformation of biomass from its feedstock, using experimental conditions more similar to those of peat formation.…”

Increasing Sustainability of Growing Media Constituents and Stand-Alone Substrates in Soilless Culture Systems

“…According to Kern et al [25], char materials must not necessarily remain on the level of a minor ingredient, but have the potential to be used as major constituents. Furthermore, since they are characterized by a high porosity and a high water-holding capacity, these materials may also be usable as a substitute for constituents, which are already established in the growing media market, but which have a limited supply [25,147,148]. For instance, rice hull-derived biochar would be a practically applicable amendment to improve the properties of growing media, in terms of an increased cation exchange capacity and water content [149].…”

Poinsettia Growth and Development Response to Container Root Substrate with Biochar

“…Other research showed that a small amendment of biochar (1 to 5% by weight) to coconut (Cocos nucifera) fiber-tuff potting root substrate improved tomato (Lycopersicum esculentum) and pepper (Capsicum annuum) growth [23]. Biochar made from sewage sludge with commercial peat-based substrate was reported to increase macronutrient content of media, increase lettuce (Lactuca sativa) biomass by 184 to 270%, increase microbial biomass by 966%, and reduce the transfer of metal concentration compared to the direct use of sewage sludge [24].…”