GHGs reduction by utilizing rice straw in steelmaking process: estimation of the effect of varying the amount of plowing

抄録

An efficient scheme to reduce greenhouse gases (GHGs) emissions more than coal replacement with general biomass was proposed. Currently, rice straw is plowed into paddy fields and emits methane, which is one of the major causes of the greenhouse effect. In this scheme, the straw is used as biomass charcoal for steelmaking.

Focusing on rice paddies and steel mills as GHGs sources, methane from straw in paddies and CO₂ from coal at steel mills are currently emitted. The use of the straw in steelworks reduces both emissions, therefore it can be a more efficient GHGs reduction scheme than the use of biomass in general.

In order to evaluate the proposed scheme, methane emissions from rice straw were calculated using the regression formula of methane emission flux estimated by DeNitrification-DeComposition-Rice model (DNDC-Rice model). The methane emissions for the current amount of straw plowed into paddies and for the case where no straw was plowed were calculated, and the difference was evaluated as the methane reductions.

Additionally, the CO₂ emissions associated with coal use were considered and it was found that the proposed scheme could reduce GHGs equivalent to 2.6 to 3.8 tons of coal per ton of coal replaced when using Global Warming Potential over 100 years (GWP-100), or 5.7 to 9.3 tons with GWP-20.

GHGs reduction for partial straw plowing was also evaluated by changing the ratio between the amount of straw plowed and used as charcoal substitute, and it was found that it remained constant regardless of the ratio.