The Greenhouse Gas (GHG) Protocol, a global standard for measuring and reporting greenhouse gas emissions, categorizes emissions into three scopes. Scope 1 emissions are a company’s direct emissions, such as fuel and chemicals (e.g., gas used by vehicles, refrigerants used to cool offices and data centers, and chemicals used to manufacture semiconductors for semiconductor companies). Scope 2 emissions are indirect emissions from purchased energy and heat that drive semiconductor manufacturing, ofﬁces, and data center operations. Scope 3 accounts for all other indirect emissions, including those that come from the supply chain, and those associated with employee business travel, commuting, logistics, purchased goods and services, and capital goods.
||Burning PFCs, chemicals, gases
||Energy to drive fabrication
||Raw materials, use of hardware
||Natural gas, diesel
||Energy for offices
||Chip manufacturing, use of hardware
|Data center operator
||Natural gas, diesel
||Energy for data centers
||Server hardware manufacturing, construction
A comparison of Scope 1, 2, and 3 emissions for chip companies, mobile vendors, and data center operators, according to the GHG protocol.
In alignment with the GHG Protocol, conducting life cycle assessments (LCAs) is one way to examine a hardware system’s total carbon emissions across its life cycle, including its production and manufacturing, transport, use, and end-of-life processing, or the construction of a data center. LCAs can provide a detailed understanding of the areas and components that contribute most to carbon emissions.
The shift toward capex emissions
Researchers looked at publicly available sustainability reports and life cycle analyses from AMD, Apple, Facebook, Google, Huawei, Intel, Microsoft, and TSMC. Their meta-analysis found that, for many use cases across the edge and cloud computing spectrum, most carbon emissions came from hardware manufacturing (capex), not operational system use (opex).
Personal devices like smartphones, desktops, and laptops contribute most of their carbon footprint through their manufacturing and use. While emissions from always-connected devices come mainly from opex consumption, emissions from battery-operated devices come mainly from manufacturing (capex). This hardware manufacturing footprint increases as devices become more powerful (having more memory, bandwidth, and/or storage).
While companies have been optimizing their devices’ hardware and software to maximize performance, they also need to focus on the increasing percentage of emissions that come from hardware manufacturing. The researchers estimate that, given the energy efﬁciency improvements from software and hardware innovation in the last decade, mobile devices, for example, would have to be used three years beyond their typical lifetime to amortize the carbon footprint created by their manufacture.
Data centers have followed a similar trend. The positive impact of renewable energy has shifted the focus on their carbon footprint almost entirely to a need to reduce capex emissions. The construction of the data center itself and manufacture of the hardware that goes into it are responsible for the majority of the data center’s carbon footprint.
Renewable energy has also had a significant impact in the hardware manufacturing sector, where semiconductor factories, for example, have shifted to renewable energy. But the meta-analysis reveals that even under optimistic projections, hardware manufacturing will still account for a large portion of hardware life cycle carbon footprints.
We need optimization at all levels
So, what can be done on the capex end? Facebook’s, Harvard’s, and ASU’s researchers suggest that it will require further work into making hardware more efficient, flexible, and scalable, from their design and manufacturing up to the software level – across the entire computing system stack.
When looking at semiconductor and other hardware manufacturing, the researchers recommend that hardware needs to be designed from the start with reducing capex emissions in mind. In addition to operational computation performance, data center buildings and hardware supply chains need to be designed with both high performance and low carbon emissions in mind. Using building and infrastructure materials with lower carbon impacts, building repairability and recyclability principles into design processes, extending the life span of hardware, and ensuring responsible end-of-life management will all be essential.
For software, optimizations to algorithms and applications that run data centers and improvements to runtime systems like schedulers, load balancing services, and operating systems can all improve both opex- and capex-related carbon footprints. The researchers also point to recent work into developing new programming languages to allow programmers to write more energy-efﬁcient code.