Up-cycling means for me that there is a material used the second time and than it generates a higher value than in the first application but by using the material its structure is so modified, that a second use with higher value is possible. I would credit this material in an LCA with the replacement of that material that is normally used for this purpose. I have no good examples for such a product.

On a sustainable standpoint, ‘upcycle’ simply means using old materials in a way that’s as good or better than the original. Way forward is  to have a holistic view of flow of energy and materials with a LCA model. 

Semi closed loop recycling wood be  good modelling

From my point of view and if I understood your question, I would break and analyse each sector of the life cycle. In the upcycle, the only thing we need to pay attention is that each material going through this upcycle sector brings its embodied  coefficients of mass, energy and impacts. Products made with those materials will embody those intensities. One could compare those materials going to be dump in a landfill with alternative uses. Some of these alternative uses can offset the impact memory of old materials. I hope I helped you.

In an LCA you model different environmental impact, and the most commonly used impact are the total CO2 eq emissions of a LCA. So to simply an example: assuming you are going to measure the CO2eq emissions from the LCA of a MSW (management system) you will have to find out: 1)the total amount of CO2 eq emissions that 1 ton (for example) of MSW produces (depending on how many levels you want to consider you can only consider the CO2eq emissions starting from the process of collecting the MSW or starting all the way back from the process of extracting the raw materials for the prodcuts that will become the MSW), and 2)the total amount of CO2 eq emissions that 1 ton of MSW saves you if it is used instead of 1 ton virgin material to produce a certain product (=re/upcycling). Then you just do 1-2=your total CO2 eq emissions

I could recommend to read the following publications if you are looking to learn more about "Upstream" / "Downstream" scope when comparing MSW management schemes by LCA.

I am not well verse with the term "upcycling" and its similarity with "Upstream"

Turconi, R., Butera, S., Boldrin, A., Grosso, M., Rigamonti, L., Astrup, T., 2011. Life cycle assessment of waste incineration in Denmark and Italy using two LCA models. J R Soc Med 29, 78–90. doi:10.1177/0734242X11417489

Finnveden, G., 1999. Methodological aspects of life cycle assessment of integrated solid waste management systems. Resources, Conservation and Recycling 26, 173–187. doi:10.1016/s0921-3449(99)00005-1

A bit outdated work, but which compares in good way different approaches concerning the allocation of recycled materials and its emissions in LCA inventories is the following publication, if you can understand German:

Kehrbaum, Ralph: Materialrückführprozesse in der Sachbilanz, Jülich : Forschungszentrum Jülich, 1997

The standard method to take in to account recycling and "upciclyng" into LCA is making a so called system expansion. System Expansion in a closed or open loop depending on the characteristics of the re or up- cycled product. System expansion explained better in ISO 14044 than in ISO 14040 but I can suggest also to read the following:

Weidema, Bo. "Avoiding co‐product allocation in life‐cycle assessment."Journal of industrial ecology 4.3 (2000): 11-33.

Cederberg, Christel, and Magnus Stadig. "System expansion and allocation in life cycle assessment of milk and beef production." The International Journal of Life Cycle Assessment 8.6 (2003): 350-356.

Please check out these articles, they might be helpful:

*Chemical recycling of plastic waste: evaluation of environmental and economic performances of gasification-and incineration - based treatment for lightweight packaging waste, Raoul Voss et al., circular economy and sustainability, 2022

*Plastic waste upcycling toward a circular economy, Xianhui Zhao et al., Chemical Engineering Journal,2022.

One manifestation of material 'upcycling' can be 'chemical recycling'. Recent studies have been published by companies like BASF, Plastic Energy, and independent think tanks like The Consumer Goods Forum that will be useful to read for this.

In the DecomBlade projec, we decided to implement LCA output, circularity and other criteria in an MCDM to consider the waste management hierarchy. we may consider a higher weight for resource depletion to represent avoiding resources.