Wednesday 21 October 2015

PCI Sustainability: The Big Picture

Jonathan Cullen of Cambridge University said the world is not about to run out of energy or materials but something must nevertheless be done to stop and even reverse the rise in anthropogenic carbon dioxide in the atmosphere.  Since 1870, human activity has added 1500 gigatonnes of CO2 to the atmosphere and this has raised global temperatures by about 1oC.  These carbon emissions have arisen in the course of improving the thermal comfort, sustenance, illumination and hygiene for the growing population; to move them and their goods around, and to make buildings, infrastructure vehicles and “things”.  With current emissions running at 28 Gt CO2/year, 35% is arising from industry, 27% from transport and 31% from buildings. 

Using Sankey diagrams to map energy flows and CO2 emissions from source to final product or service Dr Cullen showed that compared with buildings and transport, industry uses energy more efficiently.  Within industrial products, steelmaking emitted most CO2 (25%) with cement (19%), paper (4%), plastics (4%) and aluminium (3%) being the other big consumers.  However 45% of total industrial emissions were in  the Others category.  Global demand for these materials will double by 2050 and the scope for reducing their process emissions is limited by the fact that most producers are now approaching the “best practice” limits.  To reach the desirable halving of absolute COemissions by 2050, a cut of at least 75% per tonne of product is needed and this appears impractical on current technologies.

A shift from today’s “take-make-dispose” linear industry model to a restorative circular model is needed for sustainability.  Here zero waste, renewable energy use, “resilience through diversity” and products cascading through multiple uses via recycling will be the norm.  This would allow a 50% reduction in CO2 emissions per tonne of product, but of course the doubling of demand would mean zero progress in absolute emissions.  

The necessary 50% reduction in absolute emissions would need an additional 25% reduction in COemissions per tonne and this is hard to envisage.  However taking the steelmaking example this total of 75% reduction might be possible if we could:
  • Use less by design: 30% saving from putting metal only in the right place (lightweighting).
  • Reduce yield losses: ¼ of all liquid metal is scrapped in production.
  • If we can’t eliminate yield loss can we divert scrap?  i.e. Re-use without melting (maybe in construction).
  • Make products to last longer i.e. spread impacts over more time.
  • Reduce final demand by persuading consumers to buy less – an unlikely possibility with today’s politics! 
Dr Cullen also provided a progress report from Peter Levi’s (the current Cambridge PhD student) mapping of resource flows and key issues in the petrochemicals supply chain.  A map of global energy flows for 2012 showed the petrochemicals industry using twice the energy of steel production and here too, the scope for further efficiency improvements is coming to an end. The current focus of the study was on the upstream part of the chain, i.e. from natural gas and crude oil through methane, ethane, propane etc. and naphtha to the major chemical intermediates like ethylene, propylene, C4 olefins, Benzene, Toluene, Xylene, and hydrogen (see the Sankey diagram from Dr Cullen’s slides below).

The routes from these to polymers like PE, PP, PET, PAN, PA etc would come next.

World production of each chemical was being analysed by region; the initial results showing highest growth of ethylene and propylene production in the Middle East and South/Central America with declines evident in Europe and Africa.

Key questions still to be answered related to resource efficiency and prices in the petrochemical sector and establishing the historic links between energy efficiency improvement and prices.

Thinking of future price scenarios, and considering the practical limits, PCI would try to determine how much mitigation energy efficiency alone could deliver, and the resultant burden on other resource efficiency levers. 

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