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Evaluation of biogas production and operational feasibility of anaerobic co-digestion of P6 and DAF sludge from a dairy factory
(The University of Waikato, 2026) Li, Jian; Lay, Mark C.
Dairy factory wastewater treatment is commonly associated with high organic loading, energy consumption and sludge management challenges. High-strength side streams from dairy processing may contain recoverable organic energy and therefore have potential for anaerobic digestion and biogas production. This study evaluated the laboratory-scale anaerobic co-digestion feasibility of two high-strength dairy factory waste streams, P6 and dissolved air flotation (DAF) sludge, with particular focus on biogas production, pH control, chemical dosing demand, total solids/volatile solids (TS/VS) behaviour and recovery after feeding interruption. The experiment was conducted using fifteen 1 L bottle anaerobic digesters operated under mesophilic conditions at approximately 34 °C. Four linked experimental stages were used. Stage 1 was a batch start-up test under different inoculum-to-substrate (I/S) conditions. Stage 2 was a transitional operation using a fixed P6:DAF ratio of 85:15. Stage 3 was a long-term semi-continuous co-digestion stage comparing P6:DAF ratios of 80:20, 85:15, 90:10 and 95:5. Stage 4 examined shutdown, re-feeding recovery and short-term response after a second shutdown. The main analytical indicators included cumulative and interval biogas production, pre- and post-dosing pH, NaOH addition, TS/VS, VS-based apparent conversion and limited gas composition results. The results demonstrated that mixed P6 and DAF sludge could produce measurable biogas under anaerobic conditions. In Stage 1, the I/S = 1:14 group showed the highest blank-corrected cumulative biogas production and the strongest VS-added-based specific biogas response under the batch test conditions. Stage 2 helped reduce some initial differences among reactors and provided a more comparable basis for the later ratio comparison. In Stage 3, P6:DAF = 90:10 produced the highest net cumulative biogas increase, while P6:DAF = 80:20 showed strong performance and better within-group consistency. The P6:DAF = 95:5 group showed weaker net gas production and greater individual-digester variation. Stage 4 showed that residual gas production continued during shutdown and that gas production could recover after re-feeding, although recovery behaviour differed among groups and was affected by operational history and temperature disturbance in some digesters. Preliminary application of the Stage 3 results to available Tatua site-flow data indicated an estimated raw biogas flow of approximately 582–926 m³ day⁻¹, an indicative active digester volume of approximately 11,300–16,500 m³, and an apparent VS-load reduction of approximately 4.46–5.61 t day⁻¹ under the mean-flow scenarios. Because methane fraction was not continuously monitored, the gas production results were interpreted mainly as biogas production performance rather than strict methane yield. In addition, COD was not measured, and VS-based apparent conversion was treated as a relative indicator rather than a complete mass balance or biochemical conversion efficiency. Overall, the study indicates that anaerobic co-digestion of P6 and DAF sludge has technical potential for biogas production and resource recovery. However, practical implementation would require improved methane monitoring, more detailed stability indicators, longer-term operation, process optimisation and pilot-scale validation.
The right time: Women, medicine and maternal age in 1980s Aotearoa New Zealand
(BMJ, 2024) Greenhalgh, Charlotte
In the late twentieth century, increasing numbers of women in wealthy nations waited until they were aged in their 30s to give birth and become parents. This article examines responses to the changing demographics of maternity among social researchers, doctors, pregnant women and mothers in Aotearoa New Zealand. The article analyses raw research data from historical social survey projects The Right Time (interviews completed in 1982–1983) and Motherhood After 30 (1987) by the grassroots organisation the Society for Research on Women in New Zealand. Surveys, statistics and increasingly direct evidence from research participants symbolised modern social life in the mid-twentieth century. Yet, in 1966, women in Wellington, New Zealand concluded that they had been largely ignored in this endeavour. A group of volunteers pledged to produce the missing data and therefore improve policy making. This article analyses the Society’s publications and interview schedules to uncover how researchers, medics, pregnant women and mothers forged new connections between age, pregnancy and parenting during the 1980s. During this time, pregnant women advocated for a new model of prepared and mature maternity. A few years on, however, many among them identified the persistence of traditional gender roles that disrupted their plans. At the same time, physicians and public health officials in wealthy nations began to teach women to associate conception at older ages with increased risks, especially of genetic anomalies. Social research archives reveal tensions between these new, population-level recommendations and women’s proactive approaches to planning their lives and families. New Zealand’s distinctive survey records help to explain the impacts of new medical tests, reproductive technologies and public health recommendations in the context of women’s fresh approaches to maternity during the 1980s.
Exploring factors that influence the use of the paediatric early warning system : A mixed method study within the paediatric inpatient setting at Te Whatu Ora Waikato
(The University of Waikato, 2026) Clayton, Tarryn; Heath, Samantha
Background: The paediatric early warning system (PEWS) was introduced as a nationally standardised tool in New Zealand to identify and escalate clinical deterioration in the paediatric population. Although the PEWS is implemented across the country, audit data at Te Whatu Ora, Waikato indicate that there is variability to adherence to the mandatory escalation pathway. There is limited research from the New Zealand context that explores the experiences of nurses using the PEWS in practice and what factors influence decision making when using the PEWS. Objective: To explore the factors that influence nurses’ use of the PEWS assessment tool and mandatory escalation pathway in a paediatric inpatient ward at Te Whatu Ora, Waikato, and to identify any educational requirements to support the use of the PEWS. Participants: Participants were registered nurses employed in the paediatric medical ward (E5) and paediatric surgical ward (E4) at Waikato Hospital. Thirteen nurses participated in three focus groups and 31 nurses completed a quantitative survey. Methods: This research is a pragmatic exploratory mixed methods design. Phase One involved three semi structured focus groups, with data analysed using Braun and Clarke’s (2022) thematic analysis. The focus groups findings informed the development of a quantitative Likert scale survey used in Phase Two. Descriptive statistics were used to analyse the surveys, and the qualitative and quantitative findings were integrated to provide a comprehensive understanding of the factors that influence use of the PEWS. Results: Five key themes were identified: Clinical Judgement and Experience, Time Pressures, Professional Responses and Communication, Unique Factors Presented by Children, and Adherence to PEWS and Education. The survey findings validated these themes, highlighting how workload pressures, communication processes, clinical judgement, and paediatric-specific factors influence nurses’ use of the PEWS. Conclusion: Nurses view the PEWS as a valuable tool that supports patient safety, communication, and recognition of deterioration in paediatric patients. However, the use of the PEWS was influenced by factors that include the balance between clinical judgement and mandatory escalation, workload and time pressures, interprofessional communication, paediatric assessment challenges, and documentation requirements. While participants felt adequately educated in the PEWS use, education alone was not enough to ensure consistent adherence to the PEWS escalation pathways. Successful implementation requires ongoing simulation-based and interprofessional education, organisational support, adequate staffing, and understanding how clinical judgement can be utilised with the standardised pathway. These findings highlight the need for a systems-based approach to improve the use of the PEWS and enhance paediatric patient safety.
‘Our resources were ourselves’: Women and grassroots survey research in Aotearoa New Zealand, 1960s–1980s
(Berghahn Books, 2026) Greenhalgh, Charlotte; Greenhalgh, Charlotte; Corbould, Clare; Anderson, Warwick
Māori and Pākehā women in Aotearoa built a field of grassroots survey research in the 1960s to 1980s that generated extensive survey data, transformed experiences of research participation, and germinated collective, feminist and mana wāhine (the strength and power of Māori women) research methods. The first grassroots social survey organization in Aotearoa New Zealand was established in 1966 to record the unknown lives of contemporary women. Leaders of the Society for Research on Women (SROW) met while participating in the parent-led organization Playcentre, and turned their skills in collective action to the project of improving women’s lives. This was typical of Aotearoa’s voluntary ecosystem, which trained women in prominent organizations focused on families, such as Playcentre (founded in 1948), the Māori Women’s Welfare League (1951), Parents’ Centre (1951) and Te Kōhanga Reo (1982). The progressive slant of each of these national groups lowered the barriers that existed elsewhere between family-focused groups and emerging feminist and Indigenous projects. As a result, New Zealand feminists engaged closely with motherhood and early childhood education compared to their international counterparts, while Māori organizers developed world-leading approaches to language revitalization.
Design and experimental analysis of an adjustable geometry vehicle with independent drive-steering for energy efficiency optimisation
(The University of Waikato, 2026) Shang, Ray; McGuinness, Benjamin
Agricultural vehicles operating in orchard and pasture environments are required to perform frequent low-speed turning manoeuvres on uneven, grass-covered terrain - conditions under which steering strategy and vehicle geometry are major determinants of energy consumption. Despite a well-developed body of mathematical models predicting these effects, experimental validation has remained limited due to the absence of physical platforms that combine adjustable wheelbase, adjustable track width, and switchable steering strategies within a single vehicle. This thesis addresses that gap through the design, construction, and experimental evaluation of a fully electric, adjustable-geometry agricultural robot platform. The vehicle employs four independent in-wheel drive-steer modules, each integrating a brushless DC drive motor and a dedicated steering motor, mounted at the corners of a reconfigurable semi-monocoque chassis. Both wheelbase and track width can be independently adjusted across three values - 400 mm, 600 mm, and 800 mm - yielding a full 3×3 factorial matrix of nine geometric configurations. Six distinct steering modes are supported: two-wheel steering arc turn (R = 1.5 m), four-wheel steering arc turn (R = 1.5 m), skid-steer arc turn (R = 1.5 m), two-wheel point turn (R = 0), four-wheel point turn (R = 0), and skid-steer point turn (R = 0). Motor current is continuously logged at all eight drive and steer motor channels via a dedicated data acquisition system, enabling direct electrical energy quantification as E = Σ|I|·V·Δt. Controlled field experiments were conducted on two terrain conditions representative of New Zealand orchard and pasture environments: near-horizontal grass (mean inclination 0.216°) and a steep grass slope (mean inclination 17.618°). On flat terrain, all nine geometric configurations were tested across all six steering modes. On the slope, three full-width-track configurations (B = 800 mm) were evaluated for safety. Experimental results demonstrate that wheelbase L is the dominant geometric parameter governing turning energy consumption, with strong positive correlation across most steering modes (Pearson r = 0.80-0.90). Short-wheelbase configurations (L = 400 mm) consistently achieve 25-35% lower turning energy than long-wheelbase equivalents (L = 800 mm). The globally optimal configuration - B600×L400 and B800×L400 in four-wheel point-turn mode - achieves a minimum turning energy of approximately 707-710 J, representing a 31% reduction relative to the worst-performing configuration. Among all tested platforms, B800×L400 (track width 800 mm, wheelbase 400 mm, B/L = 2.00) produced the most outstanding overall performance across both flat and sloped terrain, exhibiting superior agility, smooth and rapid manoeuvre execution, and excellent directional stability, including on the 18° incline. Skid-steering modes uniformly incur the highest energy penalties across all geometric configurations (3-25× relative to the optimal equivalent mode), and a predictive L²/B parameter is shown to capture skid-steer energy with high accuracy (r = 0.86-0.98). Four-wheel steering consistently outperforms two-wheel and skid-steering strategies, and the arc four-wheel steering mode exhibits near-constant energy (~1,016 J, CV = 14%) across all nine configurations, making it the most geometrically robust steering choice. On slope terrain, arc-path manoeuvres incur substantially higher energy (+38% to +98%) relative to flat-ground equivalents due to gravitational work along the arc path, while pivot-type skid-steering energy is reduced by up to 22% due to decreased wheel-ground normal force. A systematic rearward shift in axle load distribution is identified during arc manoeuvres on slope, with rear-axle drive motors carrying up to 2.7× the energy of front-axle motors - a mechanically significant finding for rear-axle motor sizing in slope-capable platforms. Bivariate regression models of the form E = f(B, L) are derived for all six steering modes, achieving R² = 0.70-0.98 and providing practical engineering formulae for early-stage energy estimation from geometric parameters. The platform, its instrumentation methodology, and the experimental dataset collectively constitute a validated experimental foundation for steering-related energy research in electric agricultural vehicles. The findings directly inform design guidelines for energy-efficient small-scale agricultural robots, with particular relevance to orchard and vineyard applications in which turning energy represents a critical fraction of total operational energy.