Phosphorus (P₂O₅) and silicon (SiO₂) content in biomass ash. * Mean value, ** data converted with conversion factors P/P₂O₅ = 0.436, Si/SiO₂ = 0.468.

	P2O5%		SiO2%		Ref.
Biomass ash	Fly ash	Bottom ash	Fly ash	Bottom ash
Poultry litter ash	16.17*, **	11.47**	7.37*, **	19.66**	28
	—	12.16**	—	—	29
	—	22.00*, **	—	—	5
	—	19.38**	—	—	9
	22.71	—	3.19	—	30
Animal by-products (meat bone meal ash)	22.45**	25.96*, **	—	—	5
	32.50	—	1.80	—	30
Pig manure ash	—	22.80*	—	13.30*	30
Wood ash	0.69 **	3.21 **	7.69 **	12.39 **	31