Page 77 - Industrial Plants

Figure 2 - Food
waste production and
management
techniques from
1960-2017 in USA.

Figure 3: Total emissions from food waste compared to the top 20 GHG-emitting countries

Digestate typically has more nutrients and less carbon important part of the carbon sequestration mechanism
compared to compost and digestate has a higher as the carbon within the feedstock of AD is embodied
moisture content than compost. Like compost, in the digestate. Thus, adding digestate to soil
digestate can be used as a plant nutrient source in lieu effectively puts the carbon within plants back into the
of damaging synthetic fertilizers. soil, which closes the carbon cycle.
The Food waste has steadily increased in the many
The digestate is approximately 85-90% of the input counties with most of all food waste going into
biomass and is sent to a separation process to landfills.
remove the liquid portion from the solid portion.
There are different post treatment processes that AD is not only producing renewable fuel, but it is also
will produce fertilizer in powder or pellets, diverting emissions from food waste that would have
ammonium sulphate, compost, pure water. In that been sent to landfills. The Food and Agricultural
way we have a smooth disposal of the digestate Organization (FAO) of the United Nations quantified
with additional revenues and an increasing of the that global food waste produces around 4.4 GtCO2
circular economy. annually, or around 8% of total anthropogenic
greenhouse gas emissions. If food waste were its own
All of the nutrients contained with the feedstock of AD, country, it would thereby be the third largest emitting
including nitrogen, phosphorus, and potassium country in the world, after China and the United States
(collectively known as NPK), are embodied within (see Figure 3).
digestate, so it can be used as a soil amendment in
agriculture, landscaping, storm water management Removing food waste from landfills we remove the
and consumer-based horticulture. methane emissions. Considering that methane,
Moreover, introducing digestate into the soil is an compared to CO2, has a 28x higher global warming

IndustrIal Plants - September 2021
75