One of the main tasks within the LIFE 5REFRACT project is to quantify the environmental benefits associated to the new strategies for refractory waste management devised and implemented as part of the project. For this purpose, a life cycle assessment (LCA) study has been conducted. This task, led by 2.-0 LCA consultants, was carried out in two steps. As a first step, the situation for refractory waste management in the Basauri steel works at the start of the project was assessed (see blog entry of 15th May 2020), while the second step consisted of assessing the new practices in refractory waste management at the steel works as a result of implementing the 5REFRACT project, and comparing them to the previous situation. In this blog entry we tell you about this second and final step.
The LCA study addressed in both scenarios the total annual amount of refractory waste generated at the steel works, close to 6,000 tonnes/year. This includes around 4,500 tonnes of actual refractory material, plus 1,500 tonnes of lime contamination. Figure 1 shows the resulting waste management, in relative terms, excluding the 1,500 tonnes of contamination, which are ultimately destined for landfill in the two scenarios. It can be seen in this figure that total valorisation (reuse plus recycling) increases in the 5REFRACT scenario from 32% to 74%. Even though in the 5REFRACT scenario there is no direct landfilling of refractories, 26% is still indirectly discarded to landfill by the recycling plants, either due to material recovery constraints, or to recovery process inefficiencies.
Figure 1. Management of refractory waste in the Basauri steel works (approximately 4,500 tonnes/year) at the start of the project in 2018 and as a result of implementing 5REFRACT.
On the one hand, the study accounted for the environmental impacts of waste management, including waste collection, transports, treatment for recovery of secondary raw materials, and disposal of the non-recoverable fractions. On the other hand, the reuse and recycling efforts lead to the substitution of primary refractory raw materials and finished products, leading to an environmental benefit. As we saw in our blog entry on the 15th of May, the management of refractory waste at the start of the project was already leading to a net benefit, i.e. the environmental impacts of waste management are of much lower magnitude than those avoided 2018 5REFRACT Landfilled, indirect 13% 26% Landfilled, direct 55% 0% Recovered 28% 52% Reused 4% 22% by reuse and recycling. The question to be answered by the LCA in this second step was: does an additional effort in refractory waste valorisation, such as the one involved in 5REFRACT, pay off from an environmental point of view? In short, the answer is it does.
Figure 2 below shows the life-cycle greenhouse-gas (GHG) emissions associated to managing the 6,000 tonnes of annual waste generated at Basauri, breaking these emissions down according to the activities generating them, either directly or indirectly. The net difference between the 2018 and 5REFRACT scenario is around -3,900 tonnes CO2-equivalents per year, with the minus sign meaning a saving in emissions.
Figure 2. Life-cycle greenhouse-gas emissions for management of refractory waste generated in the Basauri steel works in 2018 and according to the implementation of 5REFRACT. Negative figures are interpreted as avoided emissions.
In summary, the additional effort in source-separation, collection, transport and treatment envisaged by 5REFRACT is justified in environmental terms, thanks to the avoided impact of producing new refractories, especially dead-burned magnesia (DBM), which not only requires high amounts of energy for calcination, but also releases CO2 due to the decarbonation of magnesite. However, the environmental benefit by 5REFRACT does not only concern CO2 emissions. A parallel annual saving of 28 TJ (7,778 MWh) of primary energy from fossil sources results when shifting from the 2018 management to 5REFRACT, as well as the diversion from landfill of more than 1,800 tonnes of waste per year.