Department of Architecture and Civil Engineering

Bulk use of biomass and co-fired ash in novel binders

At a glance

Funding body: Natural Environment Research Council (NERC), Resource Recovery from Waste Catalyst Grant call

Principal investigator (entire project & Bath component): Andrew Heath
Co-investigators (Bath): Richard Ball, Marcelle McManus, Kevin Paine

Partner University: Sheffield

Principal investigator (Sheffield component): John Provis
Co-investigators (Sheffield): Susan Bernal-Lopez, Hajime Kinoshita

Abstract

In order to meet climate change targets, the UK is intending to source 12% of its primary energy from biomass by 2050. European standards prohibit the use of fly ash from biomass combustion in Portland cement (PC) based concretes, the biggest current use of fly ash from coal based power generation. Unless this ash is utilised, this move from coal to biomass energy production may reduce CO2 emissions, but will increase pressure on landfill sites.

Concrete is the basis of much of the infrastructure needed for economic development, and the production of concrete with reduced environmental impact is essential in enabling the UK to meet its infrastructure needs. Concrete production accounts for 5-7% of global CO2 emissions, with the majority of these emissions coming from the production of Portland cement (PC) based binders, which are used in the vast majority of concretes.

Objectives

  • Confirm the likely quantity of biomass fly ash which will go to landfill unless a beneficial use can be found
  • Confirm that it is technically feasible to utilise natural alkalis in biomass fly ash to produce low impact concretes.

This catalyst grant project is investigating the feasibility of using biomass fly ash in novel binders called geopolymers. Geopolymers are a class of inorganic binders that can be used as an alternative to PC based binders in concrete production. They can have much lower CO2 emissions than PC based binders, and were identified by the Intergovernmental Panel on Climate Change (IPCC) as key to reducing global CO2 emissions.

Geopolymers are formed by mixing an aluminosilicate powder (typically fly ash, slags and thermally treated clays) with an alkaline activator. As biomass fly ash is naturally alkaline, there is potential to reduce activator use, further reducing CO2 emissions.