Material Matters: Definitions of Terms

These are definitions of terms used in the 2020 Waste Streams dashboard.


Bulk waste is material such as furniture, building materials, large household goods, wires, etc. that is collected and removed from small campus renovations, repair, maintenance and move-out activities. Bulk waste is transferred from campus to a facility that sorts through the material and separates out material for recycling. MIT strives to separate out recyclable materials prior to placing in bulk waste containers. Bulk waste is tracked in Material Matters and counted as a trash stream. MIT is in the process of confirming from the bulk waste processor, an approximate amount of MIT bulk waste material that is diverted for recycling.


Contamination is when material is placed into the incorrect waste stream, such as coffee cups or food waste deposited into recycling or food containers deposited into food waste only bins. Contamination may additionally occur when materials are not properly cleaned. A small amount of material contamination within a bin can decrease the quality of the entire contents of the bin or dumpster; causing all the material to be designated for trash.


Diversion rates measure the portion of waste not sent to the landfill or incineration. Tracking diversion rate over time is a great measure of the effectiveness of reuse, recycling, and food waste collection and processing.  For MIT, diversion includes mixed recycling, food waste, yard waste and re-use materials.


Diversion is the process of diverting waste from landfills or incineration through recycling, re-use and food waste collection and processing.


Food waste is an MIT waste stream category that only includes leftover food scraps. This "Food Waste" only stream is collected from about 20 locations on campus and processed off-campus via anaerobic digestion; converting the food waste into energy. During prior years, this stream was called "Compost" and included paper plates, utensils and containers which were processed on farms.  However, the region's compost streams become too contaminated with non-organic items which caused most of the collected material to become landfilled or incinerated.  MIT Facilities is testing a food waste only collection system in pilot locations on campus.  As our practices improve, we'll be changing signage and bins across campus to reflect this new Food Waste Only stream. The largest generators of campus food waste are kitchens from dining operations. 


Hard-to-recycle items include clothing, tires, mattresses, books, e-waste, and metal, which are collected in separate bins on campus. MIT engages different specialty recyclers for hauling each stream away from campus and processing and re-selling into the recycling marketplace. MIT counts these materials as diverted from landfill or incineration. We are currently seeking certifications from each specialty hauler to confirm recycling rates of these specialty streams.


Recycling is the process of converting waste into a form in which is can be re-used in the making of another product. In Material Matters data reporting, “recycling” refers to the material collected in blue bins across campus that includes mixed plastics, glass, metals and papers. It is transported from campus to a facility that sorts the materials into individual streams and seeks to sell the disaggregated streams for re-processing as industrial inputs. MIT waste audits reveal that recycling streams are often contaminated with items that do not belong.


Yard waste (grass clippings, woody materials, leaves) are collected on campus by Grounds Services and transported by a contracted waste hauler to several Massachusetts farm and open air composting facilities. Much of the yard waste is re-processed into nutrient-rich loam.