The effect of paper sludge and biochar addition on brown peat and coir based growing media properties

Hydrochars from Biosolids and Urban Wastes as Substitute Materials for Peat

“…Both values were higher than the CEC values of different biochars previously used for the preparation of growing media. For example, Nieto et al () used a biosolids biochar with CEC values ranging from 15·5 to 26 mmol (+) ·100 g −1 , while Méndez et al () used deinking paper sludge biochar with a CEC of 12·8 mmol (+) ·100 g −1 . The mixtures of hydrochars with peat lead to intermediate values (66·7 mmol (+) ·100 g −1 for PT + HSL and 53·6 mmol (+) ·100 g −1 for PT + HUW).…”

“…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.…”

“…Generally, organic waste requires aging or composting in order to be transformed into mature and stable products. More recently, biochar (the carbonaceous material obtained from biomass pyrolysis) has been trialed as a growing media component with the aim to improve peat properties (Dumroese et al, ; Kaudal et al ., 2016; Nieto et al, ; Méndez et al, ; Tian et al, ). Biochar production by thermal treatment of biomass in limited oxygen atmosphere can gradually promote the release of oxygen functional groups, while aromatization and condensation reactions with rising temperature and time lead to stable, carbon rich and structures.…”

“…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.…”

Biochars in Soils: Towards the Required Level of Scientific Understanding

“…Soil water content in soil-biochar mixtures is not always enhanced with the effects being dependent on application rate and usually with more pronounced increases in the macroporosity than the microporosity of soils (Tammeorg et al 2014a(Tammeorg et al , 2014bJeffery et al 2015b;Masiello et al 2015). The suggested use of biochar as a component of horticultural growing media (Méndez et al 2015;Vaughn et al 2015;Kern et al, this issue) makes it necessary to differentiate between soils and growing media for calculating the influence of biochar on retention of plant-available water. In the latter case, it is advisable to determine biochar water retention between -1 and -10 kPa, differentiating between easily available water (from -1 to -5 kPa) and water buffering capacity (-5 to -10 kPa).…”