Keywords

Peat alternatives; forest residual biomass; non-native species; waste-flow valorisation;

circular economy.

Abstract

Horticulture industry uses peat as the main constituent in growing media formulations

due to its ability to support efficient plant production. However, peat is a non-renewable

resource at its actual extraction rate, and environmental issues associated with

greenhouse gases emission from peat harvest raised peatland ecosystem

conservation awareness through environmental initiatives, organizations and politics

worldwide, limiting its use. There has been an increasing demand for environmentally

friendly peat alternatives focused on locally available, organic and renewable materials

from industrial side-streams, mainly wood-based and forest biomass. Therefore,

woody raw-materials physical, chemical and biological properties are important to

determinate further pre-treatment identification and choice. This work evaluates bark-

based growing media suitability from non-native forest species in Mediterranean

region, Acacia melanoxylon – residual biomass from invasive species control – and

Eucalyptus globulus – a pulpwood industrial waste-stream. Ageing, a zero-waste

treatment, allowed A. melanoxylon mature bark to effectively replace half of container

medium volume as peat alternative. Low-temperature hydrothermal treatment, a faster

process, enabled E. globulus bark to substitute quarter container medium volume,

ensuring equal plant performance as commercial material. Both raw-materials sieve

size manipulation promoted its incorporation as aeration growing media component.

Given the wood-based raw-materials nature, Nitrogen amendment should be provided

according to plant and cultivation system’s needs. Furthermore, by replacing the ‘end-

of-life’ biomass material into new potential horticultural products, circular economy

approach was applied throughout this study. Thus, A. melanoxylon juvenile bark

extracts phytotoxic effect showed a promising non-synthetic and natural bio-herbicide

for weed control. In response to the potential circularity of invasive species biomass

resources into add-value horticultural products, the present study outcome underlines

Acacia species biomass commercial valorisation as alternative management tool to

support the costs of control, avoiding the potential risk of conflict between economic

exploitation and negative environmental impact.

Keywords