The correct options are
A They need no external energy input or machinery to process the sewage.
B They are eco-friendly.
D They can produce odour.
Vermi-processing toilets use earthworms to decompose human excreta and are eco-friendly. They need no external energy input or machinery to process the sewage. They can produce odour due to reasons like inadequate ventilation, overfeeding of worms, etc. They are high maintenance since they need constant monitoring with respect to the feeding of worms, maintaining the temperature of compost, etc.