Human emissions of greenhouse gases are the primary drivers of climate change. But where do these emissions come from?
There are two popular ways and methods to categorize greenhouse gas emissions from human activities:
By source - where the overall emissions are produced.
By end use - within each source what the emissions are used for.
All of the data on both of these methods for measuring emissions can be summarised in the chart below:
Based on the chart, energy is accountable for 73% of global greenhouse emissions; ranking it to be number 1 sector that produces the most emissions. This includes emissions from producing heat and electricity, transport fuels, energy for making products, buildings, gas leaks and producing fertilizer .
Without including emissions from energy use, farming and land use change accounts for 18.3% of emissions (if we include emissions from energy use, this number is even higher!). This makes farming and land use change the next biggest source of greenhouse gas emissions after energy. Some of the farming processes that emits to greenhouse gasses includes: animals digesting their food, the break-down of manure by microbes, growing rice and tractors harvesting crops.
This sector also includes emissions from land use changes. Trees and healthy soils tend to absorb more CO₂ from the atmosphere than they release . They are what’s known as carbon sinks. But when forests are cleared for farms, roads and buildings, the carbon that is stored in them is released back into the atmosphere.
Next after agriculture is industrial processes, which accounts for 5.6% of emissions. This includes emissions from producing cement, chemicals, and various other materials (like plastics, rubber and man-made fabric). This is one of the fastest growing sources of greenhouse emissions and has grown by 174% since 1990!
Another 3.2% of human greenhouse gas emissions comes from the waste sector. Waste in landfills, sorting wastewater and treating human sewage all produce greenhouse gases, especially methane and nitrous oxide. The largest source of these comes from landfilling of solid waste, including food waste.