title: The integration of heat pumps with biomass boiler flue gas for generating hot water

authors: Muldoon, Catherine

subjects: Biomass boiler

abstract: Achieving the goal of net zero greenhouse gases by 2050 requires reducing demand and switching from fossil fuels to renewables. Process heat in New Zealand is a significant source of greenhouse gas emissions. Transitioning to biomass boilers could lower emissions and offer opportunities for waste heat recovery by integrating heat pumps with the flue gas.
This thesis evaluates heat pump integration for hot water production, supplying low temperature process heat. Using an industrial case study, a boiler model is developed and confirmed against industrial measurements. Flue gas composition is modelled to determine temperature-enthalpy profiles, and therefore the heat available for recovery and upgrade. Combustion is modelled for different biomass fuels and varying flue gas oxygen levels. The higher moisture fuels showed increased availability of heat for utilisation, which decreased as flue gas oxygen levels increased.
Three heat pump cycles are explored to maximise efficiency. Refrigerant selection is considered with respect to environmental factors and thermodynamic suitability. Using a basic cycle heat pump the three most promising refrigerants, ammonia, propane and cyclopropane, were identified and considered in more detail for the industrial case. Subcooling improved efficiency and should be maximised. An internal heat exchanger also improves efficiency and reliability and should be considered. Two zeotropic mixtures were investigated to take advantage of the temperature glide. The propane-pentane (50wt%-50wt%) blend matched the temperature profile more closely and provided increases in COP.
To make the most of the latent heat in the flue gas, the evaporator temperature must be much lower than the dew point. However, absorbing heat from low source temperatures results in lower COPs, but higher volumes of hot water generated.

text: The integration of heat pumps with biomass boiler flue gas for generating hot water Achieving the goal of net zero greenhouse gases by 2050 requires reducing demand and switching from fossil fuels to renewables. Process heat in New Zealand is a significant source of greenhouse gas emissions. Transitioning to biomass boilers could lower emissions and offer opportunities for waste heat recovery by integrating heat pumps with the flue gas.
This thesis evaluates heat pump integration for hot water production, supplying low temperature process heat. Using an industrial case study, a boiler model is developed and confirmed against industrial measurements. Flue gas composition is modelled to determine temperature-enthalpy profiles, and therefore the heat available for recovery and upgrade. Combustion is modelled for different biomass fuels and varying flue gas oxygen levels. The higher moisture fuels showed increased availability of heat for utilisation, which decreased as flue gas oxygen levels increased.
Three heat pump cycles are explored to maximise efficiency. Refrigerant selection is considered with respect to environmental factors and thermodynamic suitability. Using a basic cycle heat pump the three most promising refrigerants, ammonia, propane and cyclopropane, were identified and considered in more detail for the industrial case. Subcooling improved efficiency and should be maximised. An internal heat exchanger also improves efficiency and reliability and should be considered. Two zeotropic mixtures were investigated to take advantage of the temperature glide. The propane-pentane (50wt%-50wt%) blend matched the temperature profile more closely and provided increases in COP.
To make the most of the latent heat in the flue gas, the evaporator temperature must be much lower than the dew point. However, absorbing heat from low source temperatures results in lower COPs, but higher volumes of hot water generated.

year: 2024

title: Effects of severe cattle treading on soil physical properties and pasture productivity

authors: Zegwaard, Karsten E.

abstract: Severe cattle treading can result in compaction and pugging, of which the latter was the focus of this thesis. Pugging is one of the severest forms of treading damage to soil, and occurs when soil is grazed while near saturation, resulting in plastic and liquid soil deformation. The research objectives were to quantify effects from one-off treading events, at different severities, on soil physical properties and sward characteristics, to monitor recovery from the one-off treading event, and to develop methods of estimating potential effects of treading on pasture productivity. 
Three field experiments were carried out on a Te Kowhai silt loam soil (NZ soil classification, Typic Orthic Gley; USDA soil taxonomic classification, Typic Endoaqualj) supporting a mixed sward of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). A oneoff treading event of either O ( control), 3, 9, or 24 hours was carried out using lactating Holstein-Friesian cattle (300 cows ha- 1) at three soil moisture contents (65%, 71 %, and 81 % gravimetric soil moisture content). Soil physical properties, soil surface features, and sward characteristics were monitored for up to 34 weeks after the treading event. 
Longer treading durations at wetter soil conditions had increasingly detrimental effects on soil macroporosity, saturated hydraulic conductivity (Ksai), unsaturated hydraulic conductivity (K_40), surface roughness, depths of pug prints, bare ground area, ryegrass tiller density, and herbage accumulation. Soil dry bulk density and total porosity did not change, even under the severest of treading damage, because decreases in macroporosity were offset by increases in microporosity (r2 = 0.63; P <0.001). 
The area of bare ground increased to up to 87% of the soil surface and correlated with decreased in herbage accumulation (r2 = 0.73; P <0.001). Sward botanical composition did not change after treading damage, except when large patches of bare ground persisted into spring, resulting in the establishment of broad-leaved plantain (Plantago major L.). 
Soil and sward recovered (i.e. no significant difference compared to simultaneous controls) following treading damage and when the pasture continued to be rotationally grazed. The recovery of macroporosity, Ksat, and K_40 indicated that the soil had an increased susceptibility to further treading damage for up to 13 weeks after the initial treading event. However, soil susceptibility to direct hoof damage after a one-off severe treading damage event may persist for up to 25 weeks, as sward recovery (decreases in area of bare ground) took longer than the recovery of soil physical properties. 
When the gravimetric soil moisture content was >71 %, a three hour grazing caused a total decline of 1,100 kg OM ha- 1 in pasture productivity, however, at lower soil moisture contents grazing of ::,;3 hours was unlikely to cause significant pasture productivity decline. 
When ~50% of soil penetrations using the AgResearch Penetrometer are ~2 cm, a three hour grazing with 300 cows ha -I is likely to result in pasture productivity decline. Statistical models (multivariate regression models) were used to describe the relationship of soil physical and sward properties with pasture productivity after treading. Assuming that during the grazing rotation no further severe treading damage takes place before recovery is complete, the models can be used to estimate potential pasture productivity decline from a one-off severe treading event on a pugging susceptible Te Kowhai soil using variables measured immediately before or after cattle treading. The models with the best potential for practical applications were: 

DPP*= -1770.98 + l 96.35HR - 4.47HR2 + 32.1 lAP 	                r2 = 0.72, P <0.001
DPP = -1057.55 + 43.17BG 				                                r2 = 0.61, P <0.001
DPP = -863.78 + 179.lOSR					                        r2 = 0.78, P <0.001
DPP = -701.16- 155.89HR + 5.49HR2 + 26.61PD + 122.68SR 	r2 = 0.84, P <0.001
RT* = -6.94 + l .35HR - 0.032HR2 + 0.16AP 		                        r2 = 0.78, P <0.001
RT  = -6.10 + 0.36HR + 0.1 OAP+ 0.58SR 			                r2 = 0.80, P <0.001

Where:
DPP= total decline in pasture productivity (kg OM ha- 1) 
RT= time (weeks) required until no significant difference in herbage accumulation compared to controls 
HR = proposed or actual hours of treading 
AP = AgResearch Penetrometer results (% of readings penetrating soil by ~2 cm) immediately before treading 
BG= proportion of bare ground ('Yc,) after treading 
SR= soil surface roughness index(%) after treading 
PD= mean depth of pug prints (mm) after treading 
* = models using only pre-treading variables 

The declines in spring pasture productivity correlated with declines in macroporosity (r2 = 0.70, P <0.001) and Ksat (r2 = 0.61, P <O.OI ), complementing findings from similar treading studies carried out on soils with compaction rather than pugging damage. A Treading Field Guide was constructed, using bare ground, soil surface roughness, depth of pugging, and photography, which indicated the likely pasture productivity decline. The likely pasture productivity declines were also combined with the potential benefits of using stand-off pads to derive a cost-benefit model.

text: Effects of severe cattle treading on soil physical properties and pasture productivity Severe cattle treading can result in compaction and pugging, of which the latter was the focus of this thesis. Pugging is one of the severest forms of treading damage to soil, and occurs when soil is grazed while near saturation, resulting in plastic and liquid soil deformation. The research objectives were to quantify effects from one-off treading events, at different severities, on soil physical properties and sward characteristics, to monitor recovery from the one-off treading event, and to develop methods of estimating potential effects of treading on pasture productivity. 
Three field experiments were carried out on a Te Kowhai silt loam soil (NZ soil classification, Typic Orthic Gley; USDA soil taxonomic classification, Typic Endoaqualj) supporting a mixed sward of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). A oneoff treading event of either O ( control), 3, 9, or 24 hours was carried out using lactating Holstein-Friesian cattle (300 cows ha- 1) at three soil moisture contents (65%, 71 %, and 81 % gravimetric soil moisture content). Soil physical properties, soil surface features, and sward characteristics were monitored for up to 34 weeks after the treading event. 
Longer treading durations at wetter soil conditions had increasingly detrimental effects on soil macroporosity, saturated hydraulic conductivity (Ksai), unsaturated hydraulic conductivity (K_40), surface roughness, depths of pug prints, bare ground area, ryegrass tiller density, and herbage accumulation. Soil dry bulk density and total porosity did not change, even under the severest of treading damage, because decreases in macroporosity were offset by increases in microporosity (r2 = 0.63; P <0.001). 
The area of bare ground increased to up to 87% of the soil surface and correlated with decreased in herbage accumulation (r2 = 0.73; P <0.001). Sward botanical composition did not change after treading damage, except when large patches of bare ground persisted into spring, resulting in the establishment of broad-leaved plantain (Plantago major L.). 
Soil and sward recovered (i.e. no significant difference compared to simultaneous controls) following treading damage and when the pasture continued to be rotationally grazed. The recovery of macroporosity, Ksat, and K_40 indicated that the soil had an increased susceptibility to further treading damage for up to 13 weeks after the initial treading event. However, soil susceptibility to direct hoof damage after a one-off severe treading damage event may persist for up to 25 weeks, as sward recovery (decreases in area of bare ground) took longer than the recovery of soil physical properties. 
When the gravimetric soil moisture content was >71 %, a three hour grazing caused a total decline of 1,100 kg OM ha- 1 in pasture productivity, however, at lower soil moisture contents grazing of ::,;3 hours was unlikely to cause significant pasture productivity decline. 
When ~50% of soil penetrations using the AgResearch Penetrometer are ~2 cm, a three hour grazing with 300 cows ha -I is likely to result in pasture productivity decline. Statistical models (multivariate regression models) were used to describe the relationship of soil physical and sward properties with pasture productivity after treading. Assuming that during the grazing rotation no further severe treading damage takes place before recovery is complete, the models can be used to estimate potential pasture productivity decline from a one-off severe treading event on a pugging susceptible Te Kowhai soil using variables measured immediately before or after cattle treading. The models with the best potential for practical applications were: 

DPP*= -1770.98 + l 96.35HR - 4.47HR2 + 32.1 lAP 	                r2 = 0.72, P <0.001
DPP = -1057.55 + 43.17BG 				                                r2 = 0.61, P <0.001
DPP = -863.78 + 179.lOSR					                        r2 = 0.78, P <0.001
DPP = -701.16- 155.89HR + 5.49HR2 + 26.61PD + 122.68SR 	r2 = 0.84, P <0.001
RT* = -6.94 + l .35HR - 0.032HR2 + 0.16AP 		                        r2 = 0.78, P <0.001
RT  = -6.10 + 0.36HR + 0.1 OAP+ 0.58SR 			                r2 = 0.80, P <0.001

Where:
DPP= total decline in pasture productivity (kg OM ha- 1) 
RT= time (weeks) required until no significant difference in herbage accumulation compared to controls 
HR = proposed or actual hours of treading 
AP = AgResearch Penetrometer results (% of readings penetrating soil by ~2 cm) immediately before treading 
BG= proportion of bare ground ('Yc,) after treading 
SR= soil surface roughness index(%) after treading 
PD= mean depth of pug prints (mm) after treading 
* = models using only pre-treading variables 

The declines in spring pasture productivity correlated with declines in macroporosity (r2 = 0.70, P <0.001) and Ksat (r2 = 0.61, P <O.OI ), complementing findings from similar treading studies carried out on soils with compaction rather than pugging damage. A Treading Field Guide was constructed, using bare ground, soil surface roughness, depth of pugging, and photography, which indicated the likely pasture productivity decline. The likely pasture productivity declines were also combined with the potential benefits of using stand-off pads to derive a cost-benefit model.

year: 2006

title: Haumanu Hauora: refining public health institution policy to include Māori and climate change

authors: Masters-Awatere, Bridgette

abstract: The deepening climate crisis generates specific impacts that will exacerbate the already disproportionately negative health outcomes experienced by Indigenous people. Disparate health outcomes have not spontaneously emerged, but rather have been foreshadowed by existing inequities. This article summarizes a sample of the work from a two-year research project in Aotearoa New Zealand to understand existing policy processes and ascertain the extent to which health institutions give serious consideration to climate change impacts on Māori (Indigenous people) with health vulnerabilities. Speaking to tāngata whenua (Indigenous Māori), District Health Board (DHB) employees, and subject matter experts (SMEs), it was clear that policy processes were ad hoc and problematically silenced consistent Māori input. While research participants expressed their experiences of, and aspirations for, dealing with climate change, their voices were not evident in DHB policy development processes. The deficit within existing policy process reflects a lack of preparedness in the face of climate change. Despite clear resilience and adaptation strategies, structural change is needed to address identified disadvantages. Through a co-designed policy framework (“Haumanu Hauora”), we guide policy formation to mitigate climate change risk to Māori (and others). Central to the revised policy framework is the creation of space for both internal and external Māori voices to ensure consistent Māori input throughout the policy process. We also introduce a commissioning, refining, and monitoring stage (that includes evaluation). Haumanu Hauora considers whānau-centered healthcare knowledge, needs, resources, and aspirations, to contribute to a transformed and responsive health system. Above all, we believe that strengthening health institution responsiveness to Māori health needs is essential.

text: Haumanu Hauora: refining public health institution policy to include Māori and climate change The deepening climate crisis generates specific impacts that will exacerbate the already disproportionately negative health outcomes experienced by Indigenous people. Disparate health outcomes have not spontaneously emerged, but rather have been foreshadowed by existing inequities. This article summarizes a sample of the work from a two-year research project in Aotearoa New Zealand to understand existing policy processes and ascertain the extent to which health institutions give serious consideration to climate change impacts on Māori (Indigenous people) with health vulnerabilities. Speaking to tāngata whenua (Indigenous Māori), District Health Board (DHB) employees, and subject matter experts (SMEs), it was clear that policy processes were ad hoc and problematically silenced consistent Māori input. While research participants expressed their experiences of, and aspirations for, dealing with climate change, their voices were not evident in DHB policy development processes. The deficit within existing policy process reflects a lack of preparedness in the face of climate change. Despite clear resilience and adaptation strategies, structural change is needed to address identified disadvantages. Through a co-designed policy framework (“Haumanu Hauora”), we guide policy formation to mitigate climate change risk to Māori (and others). Central to the revised policy framework is the creation of space for both internal and external Māori voices to ensure consistent Māori input throughout the policy process. We also introduce a commissioning, refining, and monitoring stage (that includes evaluation). Haumanu Hauora considers whānau-centered healthcare knowledge, needs, resources, and aspirations, to contribute to a transformed and responsive health system. Above all, we believe that strengthening health institution responsiveness to Māori health needs is essential.

year: 2023-05-05