# Energy Recovery from Biowaste and Biomass via Gasification: A Modelling Approach

## TL;DR

This study models how biowastes like wastewater sludge and food waste can be efficiently converted into renewable fuels through gasification, showing they perform well compared to traditional biomass.

## Contribution

The study introduces a detailed equilibrium model in Aspen Plus to evaluate gasification of high-moisture biowastes and compare their performance with softwood.

## Key findings

- Steam gasification increased hydrogen content up to 53% in wastewater sludge at S/B = 0.5–0.6.
- Both biowastes achieved energy efficiencies of 60–80% despite high drying energy requirements.
- Air gasification at ER ≈ 0.1–0.2 achieved 70–80% energy efficiency with 23–27% hydrogen content.

## Abstract

The transition toward a circular bioeconomy requires efficient conversion of biogenic wastes and biomass into renewable fuels. This study explores the gasification potential of wastewater sludge (WWS) and food waste (FW), representing high moisture-content biowastes, compared with softwood (SW), a lignocellulosic biomass reference. An Aspen Plus equilibrium model incorporating the drying stage was developed to evaluate the performance of air and steam gasification. The effects of temperature (400–1200 °C), equivalence ratio (ER = 0.1–1), and steam-to-biomass ratio (S/B = 0.1–1) on gas composition and energy efficiency (EE) were examined. Increasing temperature enhanced H2 and CO generation but reduced CH4, resulting in a maximum EE at intermediate temperatures, after which it declined due to the lower heating value of the gases. Although EE followed the order SW > FW > WWS, both biowastes maintained robust efficiencies (60–80%) despite high drying energy requirements. Steam gasification increased H2 content up to 53% (WWS), 54% (FW), and 51% (SW) near S/B = 0.5–0.6, while air gasification achieved 23–27% H2 and 70–80% EE at ER ≈ 0.1–0.2. The results confirm that wet bio-wastes such as WWS and FW can achieve performance comparable to lignocellulosic biomass, highlighting their suitability as sustainable feedstocks for waste-to-syngas conversion and supporting bioenergy integration into waste management systems.