Exploring the Current Global Economy’s Major Material & Energy Flows

Each year, we extract raw resources: fossil fuels, minerals, crops and wood, shown at the very left-hand side of the diagram. Post-consumer waste is also shown here as a resource. The width of the lines is proportional to the mass flow, and the user can hover over any flow to see the exact quantity. The units are million-tonnes/yr for materials, and million-tonnes-oil-equivalent for energy flows. To start thinking at the million-tonne scale/yr, this may be a helpful reference: one million-tonne/yr is roughly the amount of bananas a mid-size country such as Germany consumes annually.

These raw resources then ‘flow’ to the right, through industry, to be processed in a series of transformations. Each vertical gray box is a node where inputs are transformed to a new product or a loss. At this high-level, each node represents a major economic sector. Energy or material losses are shown as brown off-shoots. Flows may also re-circulate within an industry, which is shown as a loop – for example, the petrochemical industry generates a large quantity of secondary reactants and by-products. Loops also show when flows return to earlier in the supply chain, such as the crop residues that result from crop harvesting and processing, and are often used back on the farm.

The flow of energy and material can be traced through the economic sectors to final consumption, at the very right-hand side of the diagram, where they are consumed as goods, or for infrastructure and transportation.

We see two main purposes for this visualization: to investigate scale, and connections.

Scale is key for setting priorities and understanding feasibility. Not shown in this diagram is human-made CO2 emissions – which amounts to 35 Gt/yr, much larger than any flow shown. If we want to think about capturing and sequestering this flow, we need a material flow of the same order of magnitude. The potential of cement as a carbon-sink has thus received attention, for good reason. Food is the largest flow, and represents one of greatest opportunities to sequester more carbon in soil as crops are grown. Food waste and crop residues are massive flows that may be utilized more efficiently, but the data quality describing where they are and what happens to them now is very poor.

One can see the volume of post-consumer waste is significant, and the vast majority ends up in landfill. Clearly, there is potential to better use this resource, but the amount of steel, plastic and paper that could be recovered cannot meet demand for these materials. The circular economy can help reduce the quantity of primary resources we extract, but it is not a panacea for decarbonization.

We can also use the diagram to investigate cross-sector connections. As most net zero plans have been designed for a single sector or company, we need to carefully think about the interactions, trade-offs, and dependencies in the physical economy during a transition. A user can click on any node and the upstream and downstream sectors that are directly connected (either as a supplier or a user/purchaser) are highlighted.

As can be seen, fossil fuels are used across all sectors. A fundamental re-structuring must occur as low-carbon resources are scaled up, with new connections, synergies and competitions emerging between sectors. For example, bio-based feedstocks may be a low-carbon resource for sectors that cannot directly electrify, such as aviation, maritime shipping and petrochemicals. As can be seen on the diagram, most bio-energy today is used in buildings as fuel. This use will need to be decreased, while advanced biorefineries that can co-generate bio-materials and biofuels are scaled-up. Currently the flow of biofuels to transportation is very small (~90 Mt-oe, compared to ~2,600 Mt-oe oil).

We believe that sectors can work together to reinforce and accelerate the transition to low-carbon resources. Sectors are physically coupled, and the feedback between sectors may lead to unexpected rates of change. One example is the build-out of renewable electricity infrastructure. This infrastructure requires minerals and metals, which are typically energy-intensive and environmentally harmful to produce. However, as more clean electricity comes online, it can be used to power mining, extraction and manufacturing with greater efficiency, to then decrease the impacts of making energy infrastructure. Electricity generation needs metals, and metals production needs electricity – with proper coordination, these sectors can work together to decouple from CO2 emissions.