Assignment 2 – Biological treatment of organic waste

Assignment 2 – Biological treatment of organic waste

Part 1 – Basic questions (4 points)

1. Definitions (0.5 point)

The focus of this assignment is on the biological treatment of organic waste.

• Provide a short definition of the two underlined terms (one sentence for each definition).

2. Composting (1.5 point)

Composting can be performed at all scales, from backyard composting to large industrial facilities. Industrial composting techniques include among others windrow composting, in-vessel batch composting, aerated static pile composting, or rotary kiln composting.

• Provide a short technical description of two of these techniques (2 x 0.5 point).
• Briefly compare the two techniques (pros and cons, 0.5 point)

3. Anaerobic digestion (2 points)

Anaerobic digestion also exists at all scales, from household digesters to large industrial facilities. The process of anaerobic digestion can be implemented in various ways: dry or wet, at mesophilic or thermophilic temperatures, in continuous or batch reactors.

• Explain the differences between: dry and wet anaerobic digestion (0.5 point); and mesophilic and thermophilic anaerobic digestion (0.5 point).
• Provide a short technical description of an actual anaerobic digestion plant (e.g. pre-treatment steps, main treatment steps, and post-treatment steps). Include in the description, the various input and output flows of the process (main products, by-products, waste). (1 point)

Part 2 – Reflection questions (5 points)

4. One waste stream, three biological treatment options… (2 points)

In this question, we want to treat sorted-at-source food waste from households in an urban area. We consider three biological treatment options: windrow composting, wet thermophilic anaerobic digestion with biogas upgrading to vehicle fuel, and “Black Solder Fly”-composting.

• Discuss the pros and cons of each treatment options. Which treatment option or mix of options do you think is “most beneficial” for the environment and society? Motivate. (2 point) Note: this is an open question; make use of your own thoughts and critical thinking.

5. Several waste streams, several biological treatment options… (3 points)

In this question, we consider four different organic waste streams (Table 1). The four waste streams have different properties (e.g. moisture, cellulose/lignin/fat contents, C/N ratio, heavy metal contents, pathogens risk, and organic pollutant contents). These differences influence the choice of treatment options.

• Based on the properties of the different waste stream, and your knowledge of biological treatments, suggest a solution to treat the four waste streams. Do you combine some of the waste streams, if so, why? How do you deal with the residues/by-products of your treatment options? How do you deal with pathogen risks or other contaminants? (3 points)

Part 3 – Formality, language and referencing style (1 point)

One point is given for good structure of the submitted report, quality of language, referencing style, handling of citations, and quality of references.

Note

• Your report should be limited to a maximum of 2-3 pages excluding reference list, tables and figures.
• It is mandatory to answer all questions.
• Use the template provided for the assignments: ASSIGNMENT TEMPLATE.docx Download ASSIGNMENT TEMPLATE.docx
• The course literature includes, among other: lecture slides, list of references provided on Canvas, and course book. You are encouraged to include extra sources of information, in particular, scientific research articles.
• Thermal treatments (pyrolysis, combustion…) are not biological treatments.

Grading

0 – 4 = Fail, possibility to re-submit assignment by end of the course, to get at best a Pass

5 – 7 = Pass

8 – 10 = Pass with distinction