I’ve heard its complicated why is that?
We need to reward recycling but also have to be careful not to double count the benefits (at the start and end of life for example). The approach under EN15978 is as follows:
- to reward “design for deconstruction” as the key driver that determines the net results over the whole life of a building
- to allocate economically, so if a product is a waste product at the end of the buildings’ life (there is no market for it, so it costs money to remove it from site rather than having some sort of scrap value) then any benefits associated with recycling that product are picked up by the next person who uses it. So essentially, recycled timber is all rewarded at the start of the building’s life. Recycled aluminium is all rewarded at the end (in net terms)
Allocation of reused products from other industries are also done economically, one example of this is recycled fly ash or blast furnace slag in concrete. Because Blast Furnace has some value, it’s not as attractive environmentally as fly ash
The rules for recycling allocation under the EN15978 methodology were initially somewhat mind-boggling for me. To understand them you will likely need to take a number of re-visits and you should try to wipe out any preconceptions you may have on recycling.
So how does it work?.
Lets start with what is included in the scope of En15978 first,
Note that Module D is actually a form of “System Expansion” and one could argue is outside of the life cycle of the building.
Before we look into recycling allocation further we also need to understand a few definitions.
Recycled content is the proportion of recycled material used to create the product, the global industry average recycled content of aluminium today is approximately 35%. This means that in 100kg of aluminium 35kg comes from old recycled aluminium and 65kg comes from new raw material.
Recycling rate is the proportion of useful material that gets sent back into the economy when the product comes to the end of its life. The global industry average recycling rate of aluminium today is approximately 57%. This means that in 100kg of waste aluminium 57kg will be recycled into new aluminium products and 43kg will be sent to landfill.
Closed loop recycling, whereby a product is recycled into the same product (e.g. steel roof panel recycled into steel reinforcement). The loop is closed because when the steel product comes to the end of its life it can be recycled into a new steel product (theoretically this can happen continually forever). Closed loop is more straightforward to calculate as the emissions are directly offset by the new product that would have been required to be made from scratch.
Open loop recycling is when the product is used to create something new (e.g. old plastic bottles recycled into carpet). The loop is open because the plastic now in the carpet required other material inputs to create the carpet and cannot be recycled further (if a process is developed that can continually recycle the plastic carpet then it becomes closed loop). We use economic allocation to understand the impacts that are being offset.
Now lets focus on a closed loop recycling example of a standalone 1000 kg of ‘General Aluminium’ modeled in eTool. Under EN15978 scope impacts under module D – Benefits and loads outside the system boundary are quantified. This includes closed loop recycling which is not directly related to the actual physical boundary or life cycle of the building.
The life cycle stages for the aluminium are shown below
Kg CO2e by LC stage for 1000kg of general aluminium
Hang on, the impacts are bigger for the 100% recycled content option???
Well, there is an initial saving in the product stage of 18,280 kg CO2e from using 100% recycled content aluminium versus using a 100% raw material. The no recovery option also gets a small advantage for transport of waste (C2) because landfill sites tend to be closer to a building than recycling sites on average. The no recovery option is also (very slightly) penalised for disposal impacts, if the aluminium is recovered it has 0 disposal impacts because it is sent to the recycling plant and these impacts are counted in the A1-A3 stage of the new aluminium product. The interesting result though is in the closed loop recycling. We have a credit applied to the aluminium that is recovered and put back in the economy. This is effectively offsetting the assumed extraction requirement for the new aluminium to be used in the (aluminium) economy – for example in the next building. Likewise aluminium that is not recovered causes a higher net demand for new aluminium. To determine the ‘credit’ or ‘penalty’ at the end of the building’s life, the net increase in new aluminium required due to the use of the aluminium in the building is calculated. In the 100% recycled content, 0% recovered the material is penalised by the equivalent mass of new aluminium which will need to be extracted to supply the next building.
Yes it may seem counter-intuitive but try to think of the world aluminium economy as a single life cycle entity. If everyone used only 100% recycled aluminium that has 0 end-of-life recycling rate (ie it ends up in landfill) then we would soon run out of recycled aluminium available. We would have to go back to using raw aluminium (maybe even start digging it back out from landfill!). By encouraging recovery of the aluminium EN15978 is trying to discourage the overall extraction of the raw material.
O.K. That wasn’t too bad
So far so good but it gets trickier! Lets imagine we have fully recycled content and fully recovered aluminium,
Well you get the best of both worlds – reduced product stage and closed loop credits right?
Wrong! Here is what happens….
Kg CO2e by LC stage for 1000kg of general aluminium
The minus CO2e credit at end of life can not be applied in this instance because you are already using 100% recycled aluminium. There is no material extraction in this case to offset and your end-of-life credit is 0. You don’t get penalised for the added extraction for the future building but you don’t get credit for it because that has already been given in the product stage. Under EN15978 there is actually a very similar amount of carbon associated with a 0% recycled/100% recovered aluminium scenario and a 100% recycled/100% recovered aluminium.
Whoa, that’s deep.
Its a tricky one and there is certainly an argument to say this is not encouraging the right behaviour but the emphasis on end-of-life treatment means that the impacts are accounted for and credit is given without double counting.
So what do we take from all of this?
Recycling content and rate is an important consideration in buildings but it is no silver bullet. Every little helps in sustainability though. Focus on the durability and deconstructability of the product over the recycled content which under EN15978 has a relatively small impact on the environmental performance.
*Note figures show are taken from eToolLCD September 2016
References: Recycling Rates of Metals, T E Graedel, 2011