Conclusions
Organic materials (algal biomass from sewage treatment
plants and citrus peels) can be used as supplements for tissue
paper manufacture. Their cellulose and hemicellulose
content allows them to be mixed with pulp in low proportions
(2.5–10%), whereas their lignin and ash contents
(62%) are also favourable. The addition of algal biomass
to paper pulp significantly increased its mechanical
strength, probably due to the binding properties of the proteins
and chitin of the algal cells. However, brightness deteriorated
severely due to chlorophyll, which acts as a natural
green dye.
The addition of citrus (orange and lemon) peels to paper
pulp had a neutral effect on breaking length, a positive
effect on bursting strength and a negative effect on tearing
resistance. Brightness was negatively affected at proportions
of 10%, because citrus peel particles behave as
coloured pigments. Overall, algal biomass seems to be a