Biogas from coffee waste

Transcrição

1 Biogas from coffee waste Two case studies Problem about 4 ton/day of coffee waste (solid content between 13 e 22%) from coffee substitutes production Inicially disposed on land

2 Waste composition Waste # coffee Barley Rye Malted Barley Chicory Eko Ricoré Pensal 1 Mokambo Tofina Other available wastes The factory has a WWTP producing 3.9 ton/day of sewage sludge (22%TS)

3 Case Study I Co-digestion of coffee waste with sewage sludge Lúcia Neves, Rosário Oliveira e Madalena Alves Batch assays of co-digestion of coffee waste and sewage sludge Experimental Conditions: 7g TS coffee waste/gts sewage sludge relative proportion of waste production 2.3 g TS waste (Coffee waste+sewage sludge)/g TS inoculum 6 to 9 % Total solids (TS) from the waste in the reactors

4 12 Results ml CH4 (PTN) eko+lamas ricoré+lamas pensal+lamas mokambo+lamas tofina+lamas Tempo, horas Results assay # Methane Production (m 3 CH 4 (STP) / kg VS initial ) methanation TS reduction VS reduction Eko Ricoré Pensal Mokambo Tofina

5 45 45 Results mg COD/L 3 15 EKO 3 15 Ricoré Maximum VFA concentration (29 g/l) mg COD/L Time, hours 45 mg COD/L Pensal Time, hours Mokambo Time, hours Tofina Soluble COD ( ), VFA ( ) CH 4 ( ). For all the assays 84 to 97 % of the initial COD was hydrolyzed, and the % of methanation was -89%, with the single exception of the barley waste which achieve just 1% of the maximum methane potential. Results assay# Eko Ricoré Pensal Mokambo Tofina Constante de hidrólise (d -1 ) The highest the hydrolysis rate the lowest the methane yield.,1 k (d -1 ),5,1,2,3 Methane yield (m 3 CH 4/kg VSinitial) Probably there was some accumulation of intermediates (aromatic compounds?) that could be potentially toxic to the methanogens.

6 Conclusions TS reduction in the range 5-73% VS reduction in the range -8% Low values of hydrolysis constants... between d-1 However hydrolysis was not the rate limiting step Barley waste only achieved 1% of the maximum methane potential and TS and VS reduction of 31 e 4%, respectively. Case Study II Enhancement of methane production from a barley waste Lúcia Neves, Raquel Ribeiro, Rosário Oliveira e Madalena Alves

7 Two strategies I) alcaline pré-hydroysis of the barley waste before the co-digestion with sewage sludge II)Co-digestion of the barley waste with kitchen waste I Alcaline pre-hydrolysis (preliminary study).3g NaOH/gTS, 24 hours, at 25º C. Followed by co-digestion with sewage sludge as previously defined. 7gST coffee wastel /gst sewage sludge 2.3gTS substrate /gst inoculum

8 Results 25 LCH4(PTN)/KgSV inicial # Tempo, dias (LCH 4(STP) / kg VS initial ) metanation ST reduction SV reduction Without pretreatment With pretreatment II - Co-digestion of coffee waste with kitchen waste + Digester I 6% of kitchen waste +4% of barley waste Digester II 1% of kitchen waste TS in both digesters: 22%

9 Results ph, TS, VS and COD ph ST (g/kg) SV (g/kg) CQO (g/l) Tempo (dias) Tempo (dias) Digester I ( ) e Digester II ( ) Results methane production 5 Mixed wastes stabilized earlier than the kitchen waste 1% L CH4 (STP)/kg VSinitia tempo (dias) % CH4 8% 6% 4% 2% % tempo (dias) Digestor I ( ) e Digestor II ( )

10 Results # I Methane production (LCH 4(STP) /kg SV initial ) 363 methanatio n 92 TS reduction 61 VS Redu ction 67 II Conclusions The pre-treatment process should be optimized, but the preliminary results confirm its potential to enhance the biodegradability of the barley waste The addition of the barley waste to an existing AD plant working with organic or kitchen waste is feasible