Preliminary work on the compression behaviour of canola straw to high density products

Abstract

In the United Kingdom (UK), the total area of canola harvested increased between 2000 and 2008 from 332,000 ha to 598,000 ha, respectively. Currently there is not a significant market for canola straw in the UK, and consequently development of a market for canola straw would add value to the gross margin of the crop at farm level. As a biomass waste product, canola straw could be used as a fuel to generate heat through combustion. However, straw exhibits a low bulk density which makes its transport more expensive than the transfer of natural gas or petroleum. Reducing the cost of collection, transport and storage of biomass through densification is thus critical to developing a sustainable infrastructure capable of working with significant quantities of raw material. This paper focuses on a preliminary study of the fundamental behaviour of canola straw under compression in closed cylindrical dies, in order to design efficient equipment for compression of biomass to solve the biomass collection, transportation and storage problem. To fulfill the aim of this paper, two main objectives were studied: 1) Definition of the pressure-density curve of the compression of canola straw and 2) Analysis of the effect of applied pressure on the measured die density and the relaxed densities and specific energies required to produce the wafers. As a conclusion of this preliminary work it has been demonstrated that canola straw can be used to produce high density products without the need of adding binders or lubricants. The specific energy required to produce the wafers, as well as the final density of the wafers, was affected by the applied pressure. Specific energies to produce 50 mm diameter wafers varied from 15.0 to 57.2 MJ t-1, depending on the pressure applied