Veronica Moset

Mesophilic versus thermophilic anaerobic digestion of cattle manure: methane productivity and microbial ecology

In this study, productivity and physicochemical and microbiological (454 sequencing) parameters, as well as environmental criteria, were investigated in anaerobic reactors to contribute to the ongoing debate about the optimal temperature range for treating animal manure, and expand the general knowledge on the relation between microbiological and physicochemical process indicators. For this purpose, two reactor sizes were used (10 m3 and 16 l), in which two temperature conditions (35°C and 50°C) were tested. In addition, the effect of the hydraulic retention time was evaluated (16 versus 20 days).

Microbial population dynamics in continuous anaerobic digester systems during start up, stable conditions and recovery after starvation

The evolution and population dynamics of complex anaerobic microbial communities in anaerobic digesters were investigated during stable operation and recovery after prolonged starvation. Three thermophilic reactor systems fed with cattle manure were operated continuously in parallel for 167days. Significant changes in the microbial communities were observed for both the bacterial and archaeal populations as the reactor systems were subjected to changing feeding regimes. The ecosystems developed from being relatively similar in structure to more specialised communities, with large population shifts within the acetogenic and methanogenic communities, which appeared to shift towards the hydrogenotrophic methanogenesis pathway. All reactor systems showed signs of adaptation to a harsher environment under high VFA, H2S and ammonia concentrations, but remained at a lower degree of stability after 45days of recovery compared to stable period of operation before starvation.

Detection of airborne Salmonella spp. in poultry farms using impingement: culture-dependent vs. culture-independent methods.

Presence of airborne Salmonella species (spp). in poultry houses can pose a risk of infection to human and animal through airborne transmission route. The objective of this study was to assess the performance of impingement technique, followed by culture-dependent and culture-independent methods to detect airborne Salmonella spp. in rooms with experimentally inoculated birds. Broilers were inoculated at 7 days of age with a marked strain of Salmonella enteritidis. The rearing cycle lasted 42 days over the summer. Airborne Salmonella spp. was weekly sampled in each room with all-glass impingers (AGI-30). Presence of Salmonella spp. was determined by three culture-dependent methods (dilutions and plating, Most Probable Number-MPN and ISO 6579:2002); and by one culture-independent method (polymerase chain reaction, PCR). Additionally, Salmonella spp. was sampled on feeders, drinkers, walls, and in the litter. No cultivable Salmonella spp. on room floor and wall, feed or litter was recovered before bird inoculation. Salmonella spp. was detected on room surfaces after inoculation, and quantified in the litter in both rooms thereafter.

Methane emission during on-site pre-storage of animal manure prior to anaerobic digestion at biogas plant: Effect of storage temperature and addition of food waste

This study investigated the temperature dependency of CH4 emission from pre-storage of animal manure prior to anaerobic digestion at 15, 20, 25 and 30 °C using lab-scale anaerobic digesters. The manure was added and removed daily to simulate the pre-storage process at biogas plants. CH4 emission accounted for 1-46% of total CH4 potential from pig manure (PM) and 1-2% of that from cattle manure (CM) at the investigated temperatures, with significant increases above 25 °C. Addition of food waste (FW) reduced the CH4 emission when storage temperature was 20 °C or lower for PM and 25 °C or lower for CM due to volatile fatty acid accumulation and lower pH (<5.5) but emissions increased with higher storage temperatures.

Improved anaerobic biodegradability of wheat straw, solid cattle manure and solid slaughterhouse by alkali, ultrasonic and alkali-ultrasonic pre-treatment

ABSTRACT Wheat straw and animal wastes are important feedstock for biogas production in Europe. Yet, the high content of lignocellulosic and refractory materials causes the process to be relatively slow. Therefore, pretreatment methods have been proposed to shorten the hydrolysis phase. The present study examined the effectiveness of alkali pre-treatment (AP), ultrasonic pre-treatment (UP), and alkali-ultrasonic pre-treatment (AUP) applied on wheat straw (WS), solid fraction of cattle manure (SCM) and solid fraction of slaughterhouse waste (SSHW), by monitoring solubilisation ratio, anaerobic biodegradability and methane yield. The results indicate that the solubilisation ratio of the substrates improved regardless of the types of pre-treatment applied. Though, AP was more effective on WS and SSHW than other pre-treatments (UP and AUP), with approximately 47% and 17% extra methane, respectively. Moreover, AP of SCM caused an increased in methane production rate by 100% and minimised lag phase from 16 days to 1 day during anaerobic digestion. Based on Danish conditions, only AP of WS was economical prior to the biogas process due to high extra methane yield. A positive energy budget of 8 € t−1 VS was calculated. High-energy consumption during UP and AUP in laboratory scale hindered the positive benefits of these pre-treatments. GRAPHICAL ABSTRACT

Modelling methane emission mitigation by anaerobic digestion: effect of storage conditions and co-digestion

ABSTRACT In this work the methane conversion factor (MCF) of untreated and anaerobically digested cattle manure (CM) as a function of storage temperature, time and co-digestion was measured in an in vitro experiment and modelled based on IPCC (2006) methodology (Tier 2). For this, one sample of untreated CM, one sample of mono-digested CM and three samples of CM co-digested with grass were incubated at seven different temperatures (from 5°C to 50°C) over 346 days. The main results showed that ultimate methane yield (B0) of CM is higher than the B0 reported by the IPCC (2006). Two temperature ranges should be considered for MCF evolution, below 15°C very low MCF was measured in this work for untreated CM, mono and co-digested samples. At higher temperatures, MCF obtained in this work and that provided by the IPCC could be comparable depending on storage time. Anaerobic mono-digestion decreased MCF compared to untreated CM at all temperatures and times, except in the temperature range between 20°C and 25°C if storage time is low, due to a lag phase observed in CM. This lag phase would probably not happen in real storage conditions depending on the proportion of old manure remaining in the storage tank. Co-digestion with grass-decreased MCF compared to mono-digestion, but increased CH4 production in terms of fresh matter due to the higher B0 of the mixture. Storage time, temperature and co-digestion should be considered in the quantification of CH4 emission from digested material.

In-situ injection of potassium hydroxide into briquetted wheat straw and meadow grass – Effect on biomethane production

Alkaline pretreatment of lignocellulosic biomass has been intensively investigated but heavy water usage and environmental pollution from wastewater limits its industrial application. This study presents a pretreatment technique by in-situ injection of potassium hydroxide concentrations ranging from 0.8% to 10% (w/w) into the briquetting process of wheat straw and meadow grass. Results show that the biomethane yield and hydrolysis rate was improved significantly with a higher impact on wheat straw compared to meadow grass. The highest biomethane yield from wheat straw briquettes of 353mL.g-1 VS was obtained with 6.27% (w/w) potassium hydroxide injection, which was 14% higher than from untreated wheat straw. The hydrolysis rates of wheat straw and meadow grass increased from 4.27×10-2 to 5.32×10-2d-1 and 4.19×10-2 to 6.00×10-2d-1, respectively. The low water usage and no wastewater production make this a promising technology.

Increasing energy and lysine in diets for growing-finishing pigs in hot ENVIRONMENTS: a preliminary study of the consequences on productive performance, slurry composition and gas emission

The influence of dietary factors on manure composition and gas emission was studied in pigs. A total of 128 pigs weighing 63.1±9.67 kg were divided by weight and sex into two dietary treatments: one high (HD) and other low (LD) in energy and lysine, but maintaining lysine:energy ratio (LD; 13.97 MJDE kg-1, 0.72 g lysine MJ-1DE and HD; 14.39 MJDE kg-1, 0.77 g lysine MJ-1DE). Average daily gain and daily feed intake were controlled during 41 days (phase 1). After the productive study, 12 females of 103.3±3.15 kg (6 per treatment) were selected and housed individually (phase 2). Feces and urine (slurry) were collected during 3 consecutive days. After collection, slurry was pooled by treatment and six 30L buckets (3 per treatment) were filled and stored during a 11-day period. Initial and final composition (dry matter (DM), organic matter (OM), total Kjeldahl nitrogen (TKN), volatile fatty acids (VFA) and pH) were analyzed. Gas emission was measured using a photoacoustic gas monitor. Both, males and females fed HD diets grew more efficiently than pigs fed LD diets (p<0.05). Slurry from pigs fed LD diets showed greater DM, OM, TKN and VFA concentrations and a lower final pH than slurry from HD pigs (p<0.05). Carbon dioxide and ammonia emission did not differ between treatments. Thus, the combination of high energy and lysine content used in the present study for growing pigs (HD) led to a more efficient growth and a lower nutrient concentration in slurry, with no significant differences in gas emission.